Two Englishmen down under developing a cannon (3-3)
I believe the answer is:
pom-pom
'cannon' is the definition.
(I've seen this before)
'two englishmen' is the wordplay.
'two englishmen' means two replacements for 'englishman'.
'englishman' becomes 'pom' (pom is an Australian term for an English person).
'englishman' becomes 'pom' (pom is an Australian term for an English person).
'pom'+'pom'='POM-POM'
'down under developing a' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for pom-pom that I've seen before include "Form of dahlia" , "Variety of dahlia" , "Ball of tufted wool, on a hat perhaps" , "Fluffy decorative ball" , "Anti-aircraft cannon - woolly ball" .)