Frantic effort by the Gunners (5)
I believe the answer is:
rabid
'frantic' is the definition.
(thesaurus)
'effort by the gunners' is the wordplay.
'effort' becomes 'bid' (bid is a kind of effort).
'by' means one lot of letters go next to another.
'the gunners' becomes 'RA' (Royal Artillery).
'bid' after 'ra' is 'RABID'.
(Other definitions for rabid that I've seen before include "Infected with hydrophobia" , "Ferocious" , "Extremely fanatical" , "Raging (having been bitten by a dog?)" , "Zealous" .)