The sentence by itself is ambiguous without context since articles are mandatory (except in front of a person's name where they are forbidden) and even with the definite article the sentence can have a general meaning, referring to all English clocks in existence. In English you can tell since the article is optional and clarifies if the meaning is specific or general.
Milyen órát szeretnél a nappaliba? Jó lenne egy angol óra?
Az angol órák kicsik, én valami nagyobbat szeretnék.
What kind of clock would you like in the living room? Would an English clock be ok?
English clocks are small, I would like something bigger.
Van egy pár angol óránk a padláson.
Kellene helyet csinálnunk a padláson.
Az angol órák kicsik.
Elférnének máshol is.
We have a couple English clocks in the attic.
We need to make room in the attic.
The English clocks are small.
They could fit elsewhere.
Thank God I am a Spanish native speaker and hence (and from what I can see) I don't have the same struggles with the article "a/az" (as English speakers do), since it seems we use it just the same way ^^ . [No offence intended of course, it's just cool to see some similarities with my mother tongue =D .]
Actually the indefinite article "a / an" in English does a similar thing, and you use context or reason to resolve the ambiguity.
"An eagle is a beautiful bird" - actually a general statement equivalent to "Eagles are beautiful birds."
"An eagle is on the roof" - there is a specific eagle on the roof, and this sentence is not a general statement about all eagles.
It's like that with the Hungarian definite article, too.
This sort of thing gives computer translation programs enormous difficulty, but we just figure it out.