Put in again, checks unlikely (9)
I believe the answer is:
reinstall
'put in again' is the definition.
(I've seen this before)
'checks unlikely' is the wordplay.
'checks' becomes 'reins' (reining is a kind of checking).
'unlikely' becomes 'tall' (I've seen this in another clue).
'reins'+'tall'='REINSTALL'
(Other definitions for reinstall that I've seen before include "Replace" , "Again establish" , "Put back in" , "begin program again" .)