All I give in return for watch? Not all (5)
'watch? not all' is the definition.
I can't judge whether this defines the answer.
'all i give in return' is the wordplay.
'in' indicates a hidden word.
'return' says the letters should be written in reverse.
'ligiv' is hidden in the letters of 'all i give'.
'ligiv' reversed gives 'VIGIL'.
'for' acts as a link.
(Other definitions for vigil that I've seen before include "Period of staying awake to watch or pray", "period of wakefulness", "observance", "Watch maintained at night", "Night-time watch".)