Acquire information to retain control (4)
I believe the answer is:
rein
'control' is the definition.
(I know that rein is a type of control)
'acquire information to retain' is the wordplay.
'to retain' indicates a hidden word (I've seen 'retaining' mean this).
'REIN' can be found hidden inside 'acquire information'.
(Other definitions for rein that I've seen before include "Part of tack" , "given free to experienced riders?" , "A means of control" , "Hold back" , "one's attached to a bit" .)