Available buyer securing new ship (6)
I believe the answer is:
tanker
'ship' is the definition.
(ship carrying liquids)
'available buyer securing new' is the wordplay.
'available buyer' becomes 'taker' ('any takers?').
'securing' indicates putting letters inside.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'taker' placed around 'n' is 'TANKER'.
(Other definitions for tanker that I've seen before include "Oil-carrier" , "Ship or vehicle to carry crude oil" , "Bulk-carrying ship" , "Liquid-carrying vehicle" , "Bulk-liquid lorry" .)