Officer agitatedly enrages troops to begin (8)
I believe the answer is:
sergeant
'officer' is the definition.
(sergeant is a kind of officer)
'agitatedly enrages troops to begin' is the wordplay.
'agitatedly' indicates an anagram (I've seen this in other clues).
'to begin' indicates taking the first letters.
The initial letter of 'troops' is 't'.
'enrages' anagrammed gives 'sergean'.
'sergean'+'t'='SERGEANT'
(Other definitions for sergeant that I've seen before include "Police rank" , "officer of the law" , "Pepper, say" , "Army rank" , "Man in charge" .)