Organised gunners by name (3)
I believe the answer is:
ran
'organised' is the definition.
(I've seen this in other clues)
'gunners by name' is the wordplay.
'gunners' becomes 'ra' (Royal Artillery).
'by' means one lot of letters go next to another.
'name' becomes 'n' (common abbreviation e.g. on forms).
'ra'+'n'='RAN'
(Other definitions for ran that I've seen before include "Managed; raced" , "Entered (a race)" , "Managed; hurried" , "Sprinted" , "Took a single" .)