Parking, say, behind club (6)
I believe the answer is:
putter
'club' is the definition.
(putter is a kind of club)
'parking say behind' is the wordplay.
'parking' becomes 'p'.
'say' becomes 'utter' (I've seen this before).
'behind' means one lot of letters go next to another.
'p'+'utter'='PUTTER'
(Other definitions for putter that I've seen before include "Club used on the green" , "Club to use on the green" , "Type of golf club" , "Golf club used on greens" , "Golf-club" .)