Take back worker on sports ground (6)
I believe the answer is:
recant
'take back' is the definition.
(I've seen this in another clue)
'worker on sports ground' is the wordplay.
'worker' becomes 'ant' (worker is a type of ant).
'on' means one lot of letters go next to another.
'sports ground' becomes 'rec' (abbreviation for recreation ground).
'ant' put after 'rec' is 'RECANT'.
(Other definitions for recant that I've seen before include "Withdraw a former declaration" , "Go back on a statement of belief" , "Revoke a former declaration" , "Abjure, forswear" , "announce change of view" .)