Get at Arsenal, no wingers, vague, no guts (7)
I believe the answer is:
unnerve
'get at' is the definition.
(get at can mean to unnerve or worry)
'arsenal no wingers vague no guts' is the wordplay.
'arsenal' becomes 'gunnery' (both can mean a place guns are made or kept).
'no wingers' indicates the central letters (letters on the wings of the word are removed).
'no guts' says to hollow out the word (remove centre letters) (the guts of the word are removed).
The centre of 'gunnery' is 'unner'.
'vague' with its centre removed is 've'.
'unner'+'ve'='UNNERVE'
(Other definitions for unnerve that I've seen before include "Deprive of courage" , "Frighten" , "Intimidate" , "Perturb" , "Dishearten - discourage" .)