Vessel filled with hock for fathers (6)
I believe the answer is:
spawns
'for fathers' is the definition.
(father can mean to create or spawn)
'vessel filled with hock' is the wordplay.
'vessel' becomes 'SS' (prefix in ship names eg SS Great Britain).
'filled with' means one lot of letters goes inside another.
'hock' becomes 'pawn' (synonyms).
'ss' going around 'pawn' is 'SPAWNS'.
(Other definitions for spawns that I've seen before include "Leads to man" , "produces offspring" , "Deposits eggs like fish or frogs." , "Makes large numbers" , "Of fish, lays eggs" .)