Put back controls, seemingly unbelievable (9)
I believe the answer is:
reinstall
'put back' is the definition.
(I've seen this before)
'controls seemingly unbelievable' is the wordplay.
'controls' becomes 'reins' ('rein' can be a synonym of 'control').
'seemingly unbelievable' becomes 'tall' (as in a tall tale).
'reins'+'tall'='REINSTALL'
(Other definitions for reinstall that I've seen before include "Replace" , "Put back in" , "Again establish" , "begin program again" .)