UN and British navy invade but are not fired (7)
I believe the answer is:
unburnt
'un and british navy invade but' is the definition.
I can't judge whether this defines the answer.
'not fired' is the wordplay.
'not' becomes 'un' (prefix meaning 'not').
'fired' becomes 'burnt' (I've seen this in another clue).
'un'+'burnt'='UNBURNT'
'are' acts as a link.
Can you help me to learn more?
(Other definitions for unburnt that I've seen before include "Not consumed by fire" , "saved from fire" , "Having escaped fire" , "what's not yet consumed" .)