Underwear found in shops aboard ship (6)
I believe the answer is:
smalls
'underwear' is the definition.
(I've seen this before)
'shops aboard ship' is the wordplay.
'shops' becomes 'mall'.
'aboard' is an insertion indicator.
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'mall' inserted into 'ss' is 'SMALLS'.
'found in' is the link.
(Other definitions for smalls that I've seen before include "Underclothes" , "Slips perhaps" , "Undies" , "Undersized underwear?" , "Diminutive undergarments?" .)