Translation:The singer is thin.
Technically both ㅅ and ㅆ have an "s-h" sound, but the double one sounds less breathy
Oh... Cause I've read(or heard. I forgot) somewhere that said the doubled one was't pronounced as 'sh' like its 'single' friend.
Yeah it's closer to that sound but there is still a faint "sh" sound. As a beginner it is probably better to just pronounce it like "s" for now. You can change it later if you need to/if you meet a Korean.