Club, say, trailing leader of Premiership (6)
I believe the answer is:
putter
'club' is the definition.
(a golf club)
'say trailing leader of premiership' is the wordplay.
'say' becomes 'utter' (I've seen this before).
'trailing' says to put letters next to each other.
'leader of' indicates taking the first letters.
The initial letter of 'premiership' is 'p'.
'utter' put after 'p' is 'PUTTER'.
(Other definitions for putter that I've seen before include "Club to use on the green" , "Golf-club" , "Club used on the green" , "Type of golf club" , "Golf club used on greens" .)