Enthusiastic call in support of gunners (6)
I believe the answer is:
raring
'enthusiastic' is the definition.
(as in 'raring to go')
'call in support of gunners' is the wordplay.
'call' becomes 'ring' (synonyms).
'in support of' says to put letters next to each other (I've seen this in other clues).
'gunners' becomes 'ra' (Royal Artillery).
'ring' after 'ra' is 'RARING'.
(Other definitions for raring that I've seen before include "Eager (to go?)" , "Eager, impatient" , "Very keen (to go?)" , "Very eager (to do something)" , "Agog" .)