Some squirrel monkeys in wood (3)
I believe the answer is:
elm
'wood' is the definition.
(elm is a type of tree)
'some squirrel monkeys in' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'ELM' can be found hidden inside 'squirrel monkeys in'.
(Other definitions for elm that I've seen before include "Source of timber" , "It provides shade" , "Hard wood" , "wood used in pelmets" , "Leaving body" .)