Maybe sloth aids half-seen mount (5)
I believe the answer is:
sinai
'mount' is the definition.
(I've seen this before)
'maybe sloth aids half-seen' is the wordplay.
I cannot really see how this works, but
'sloth' could be 'ai' (ai is a kind of sloth) and 'ai' is present in the answer.
The remaining letters 'sin' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for sinai that I've seen before include "Mountainous peninsula in Egypt" , "Law handed down here" , "11 Across peninsula" , "Biblical mount" , "Ten Commandments mountain" .)