Crook messed with ABM in secret planning location? (4,4)
I believe the answer is:
back room
'secret planning location?' is the definition.
(as in back room plans)
'crook messed with abm' is the wordplay.
'messed with' indicates an anagram.
'crook' anagrammed with 'abm' can make 'BACK ROOM'.
'in' acts as a link.
(Other definitions for back room that I've seen before include "Place where secret deals are done" , "where secrets are discussed" , "support operation" , "Place where secret or supporting work is done" .)