Tan wide part of leg (4)
I believe the answer is:
whip
'tan' is the definition.
(both can mean to hurt as a punishment)
'wide part of leg' is the wordplay.
'wide' becomes 'w' (abbreviation e.g. in cricket).
'part of leg' becomes 'hip' ('hip' is part of 'leg').
'w'+'hip'='WHIP'
(Other definitions for whip that I've seen before include "Cat-o'-nine-tails" , "Instrument of discipline" , "The one who enforces discipline in a political party" , "Party official; punish" , "Party disciplinarian" .)