Pushing, holding part of leg (4)
I believe the answer is:
shin
'part of leg' is the definition.
(I know that shin is part of lower leg)
'pushing holding' is the wordplay.
'holding' indicates a hidden word.
'SHIN' is hidden within 'pushing'.
(Other definitions for shin that I've seen before include "Part of the lower leg" , "Leg-bone" , "Cut of beef; part of leg" , "Bone at front of lower leg" , "letter from Israel" .)