Stumbles concerning a golfer (5)
I believe the answer is:
reels
'stumbles' is the definition.
'concerning a golfer' is the wordplay.
'concerning' becomes 're' (both can mean on a particular topic).
'a golfer' becomes 'els' (Ernie Els - former number one professional golfer).
're'+'els'='REELS'
(Other definitions for reels that I've seen before include "Spools" , "Bobbins" , "Staggers about in lively dances" , "Scottish dances" , "Totters" .)