Pressure applied to speak in golf club (6)
I believe the answer is:
putter
'golf club' is the definition.
(I've seen this before)
'pressure applied to speak' is the wordplay.
'pressure' becomes 'p' (abbreviation).
'applied to' means one lot of letters go next to another.
'speak' becomes 'utter' ('utter' can be a synonym of 'speak').
'p'+'utter'='PUTTER'
'in' is the link.
(Other definitions for putter that I've seen before include "Golf-club" , "Club to use on the green" , "Club used on the green" , "Golf club used on greens" , "Type of golf club" .)