One offering shot of weapon to stop outlaw (6)
I believe the answer is:
barman
'one offering shot' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'weapon to stop outlaw' is the wordplay.
'weapon' becomes 'arm' (synonyms).
'to stop' indicates putting letters inside (inserted letters plug or stop a gap).
'outlaw' becomes 'ban' (banning is a kind of outlawing).
'arm' put into 'ban' is 'BARMAN'.
'of' is the link.
Can you help me to learn more?
(Other definitions for barman that I've seen before include "He serves drinks" , "Bloke at counter" , "Pub employee" , "One employed to serve" , "Drinks server" .)