A regiment prepared to shoot (9)
I believe the answer is:
germinate
'shoot?' is the definition.
('germinate' can be a synonym of 'shoot')
'a regiment prepared' is the wordplay.
'prepared' indicates an anagram.
'a'+'regiment'='aregiment'
'aregiment' anagrammed gives 'GERMINATE'.
'to' acts as a link.
(Other definitions for germinate that I've seen before include "(Of seeds) sprout" , "Sprout - develop" , "Mere giant (anag) - start to grow" , "Sprout as in a regiment" , "Spring up" .)