Friend to declare carry-on (7)
I believe the answer is:
palaver
'carry-on' is the definition.
Both the definition and answer are singular nouns.
Maybe they are linked in a way I don't understand?
'friend to declare' is the wordplay.
'friend' becomes 'pal' (pal can mean a friend).
'to declare' becomes 'aver' (averring is a kind of declaring).
'pal'+'aver'='PALAVER'
Can you help me to learn more?
(Other definitions for palaver that I've seen before include "Song and dance" , "Powwow - a lot of fuss" , "Song-and-dance" , "Fuss and bother" , "Idle copious talk" .)