Injure with many an objective (4)
I believe the answer is:
maim
'injure' is the definition.
(to maim is to hurt or injure)
'with many an objective' is the wordplay.
'with' means one lot of letters go next to another.
'many' becomes 'M' (Roman numeral for a thousand).
'an objective' becomes 'aim' (synonyms).
'm'+'aim' is 'MAIM'.
(Other definitions for maim that I've seen before include "Injure or harm severely" , "Hurt badly" , "Injure and cripple" , "Wound so that part of body is permanently damaged" , "Wound and cripple" .)