Member of whole group (3)
I believe the answer is:
leg
'member' is the definition.
(member can mean a limb)
'of whole group' is the wordplay.
'of' indicates the answer is hidden within the clue.
'LEG' is hidden in the letters of 'whole group'.
(Other definitions for leg that I've seen before include "prop" , "Run < on" , "Lower limb" , "Support; cricket side" , "Stage (of race)" .)