A society having a whip round for a vessel (7)
I believe the answer is:
warship
'for a vessel' is the definition.
(warship is a kind of vessel)
'a society having a whip round' is the wordplay.
'society' becomes 'rs' (I can't explain this - if you can you should believe this answer much more).
'having' says to put letters next to each other.
'round' is an insertion indicator.
'a'+'rs'='ars'
'ars' inserted within 'whip' is 'WARSHIP'.
Can you help me to learn more?
(Other definitions for warship that I've seen before include "It's armed at sea" , "Eg, destroyer, cruiser" , "Navy asset" , "Naval asset" , "Fighting vessel" .)