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' is a charade indicator (letters next to each other).
'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" .)