Hand on new piece (4)
I believe the answer is:
pawn
'piece' is the definition.
(pawn is a kind of chess piece)
'hand on new' is the wordplay.
'hand' becomes 'paw' (synonyms).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'paw'+'n'='PAWN'
(Other definitions for pawn that I've seen before include "Get ready for" , "Give as security" , "Deposit as pledge" , "The foot-soldier in chess" , "one used by another" .)