Crumbled in golf on series of holes (6)
I believe the answer is:
ground
'crumbled' is the definition.
(I've seen this before)
'golf on series of holes' is the wordplay.
'golf' becomes 'g' (phonetic alphabet: alpha, bravo, charlie etc.).
'on' says to put letters next to each other.
'series of holes' becomes 'round' (a round of golf).
'g'+'round'='GROUND'
'in' acts as a link.
(Other definitions for ground that I've seen before include "Powdered; land" , "Earth; stadium" , "crumbled" , "Oval, for example" , "Earth; crushed to powder" .)