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' can be anagrammed to 'ORDNANCE'.
However, I am not clear how this is indicated.
'the' acts as a 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" .)
