Red canon joining the artillery (8)
I believe the answer is:
ordnance
'artillery' is the definition.
(synonyms)
'red canon joining' is the wordplay.
'red canon' anagrams to 'ORDNANCE'.
Though, I'm not clear how the anagram is indicated.
'the' is the link.
Can you help me to learn more?
(Other definitions for ordnance that I've seen before include "Arsenal's big guns" , "regulation" , "weaponry" , "Military supplies and materials" , "Survey may follow this" .)