Not all little angels are sylph-like (4)
I believe the answer is:
lean
'sylph-like' is the definition.
Both the answer and definition are adjectives. Perhaps there's a link between them I don't understand?
'not all little angels are' is the wordplay.
'not all' indicates the answer is hidden within the clue (only some of the letters).
'LEAN' is hidden within 'little angels are'.
Can you help me to learn more?
(Other definitions for lean that I've seen before include "Incline; without fat" , "Wiry" , "Spare - incline" , "Slim; veer" , "bank" .)