Club's players holding title regularly hunkered down (8)
I believe the answer is:
squatted
'hunkered down' is the definition.
The answer and definition are different parts of speech. However, adjectives and past participle verbs sometimes mean the same thing.
'club's players holding title regularly' is the wordplay.
'club's players' becomes 'squad' (I am not sure about this - if you are sure you should believe this answer much more).
'holding' is an insertion indicator.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternating letters of 'title' are 'tte'.
'squad' enclosing 'tte' is 'SQUATTED'.
Can you help me to learn more?
(Other definitions for squatted that I've seen before include "Sat on one's heels" , "Took temporary possession of unoccupied building, or crouched" .)