Measure some chinchillas (4)
I believe the answer is:
inch
'measure' is the definition.
(inch is a unit of length)
'some chinchillas' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'INCH' is hidden in the letters of 'chinchillas'.
(Other definitions for inch that I've seen before include "nose" , "She led the Iceni; bade ciao (anag.)" , "One 63,360th of a mile" , "Move in tiny increments" , "Move by small amounts" .)