Put off playing a certain sport (13)
I believe the answer is:
procrastinate
'put off' is the definition.
(I've seen this in another clue)
'playing a certain sport' is the wordplay.
'playing' is an anagram indicator.
'a'+'certain'+'sport'='acertainsport'
'acertainsport' anagrammed gives 'PROCRASTINATE'.
(Other definitions for procrastinate that I've seen before include "Defer action" , "Delay, waste time" , "Dilly-dally" , "Delay taking action" , "Put off what should be done now" .)