Start in place for shooting (5)

I believe the answer is:
onset
'start' is the definition.
(both can mean the beginning of something)
'place for shooting' is the wordplay.
'place' becomes 'set' (synonyms).
'for' says to put letters next to each other (I've seen this in other clues).
'shooting' becomes 'on' (I can't explain this - if you can you should believe this answer much more).
'set' after 'on' is 'ONSET'.
'in' is the link.
Can you help me to learn more?
(Other definitions for onset that I've seen before include "Beginning (of disease etc)" , "Stone (anag)" , "First signs" , "Appearance of" , "Cast stone in attack" .)
