This can mean evening or dinner
Same with 아침. Breakfast or morning.
Usually by itself 저녁 will mean evening, if you say 저녁밥 it will often mean dinner (literally evening meal/rice)
I personally never say 저녁밥. 저녁 is enough.
So would you say something like 전녁을 먹어요?
Yes, that's acceptable. Also saying 아침을 먹어요 is acceptable in place of 아침밥 or 아침식사.
When they prononce 저 녁 , can we hear the ㄱ at the end?
Barely! This has been a concern for me too but they deal with it in an episode/ a lesson of Talk To Me In Korean. They explain that the last consonant is a bit muted, so "cap" sounds like "ca" with an abrupt closing of the mouth....
A friend of mine once wanted to write a simple letter to her korean teacher. She wrote 저년 (which is a bad word) instead of 저녁 haha. The poor teacher was confused
저녁 + 식사 = dinner too
아침/점심 + 식사 = breakfast/lunch too