Army officer and I gallivant in shrub (9)
I believe the answer is:
brigadier
'army officer' is the definition.
(I've seen this before)
'i gallivant in shrub' is the wordplay.
'gallivant' becomes 'gad' ('gad' can be a synonym of 'gallivant').
'in' is an insertion indicator.
'shrub' becomes 'brier' (brier is a kind of shrub**).
'i'+'gad'='igad'
'igad' placed within 'brier' is 'BRIGADIER'.
'and' acts as a link.
(Other definitions for brigadier that I've seen before include "Military leader" , "Officer in charge of army unit, part of division" , "Air bridge over to the military officer" , "Army rank" , "Rank above colonel" .)