Golf club supporters smile occasionally (7)
I believe the answer is:
brassie
'golf club' is the definition.
(I've seen this before)
'supporters smile occasionally' is the wordplay.
'supporters' becomes 'bras' (a bra gives support to breasts).
'occasionally' indicates alternate letters (letters taken at regular intervals or occasions).
The alternate letters of 'smile' are 'sie'.
'bras'+'sie'='BRASSIE'
(Other definitions for brassie that I've seen before include "Old golf club" , "Golf-club" , "old wood" , "Number two wood (golf)" .)