Shopping area aboard ship supplies underwear (6)
I believe the answer is:
smalls
'underwear' is the definition.
(type of underwear)
'shopping area aboard ship' is the wordplay.
'shopping area' becomes 'mall' (shopping mall).
'aboard' is an insertion indicator.
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'mall' placed within 'ss' is 'SMALLS'.
'supplies' is the link.
(Other definitions for smalls that I've seen before include "Underwear (colloq.)" , "Undies" , "Undersized underwear?" , "Diminutive items of underwear" , "Diminutive articles of underwear?" .)