On ship notice pig taken inside (6)
I believe the answer is:
aboard
'on ship' is the definition.
(aboard a ship)
'notice pig taken inside' is the wordplay.
'notice' becomes 'ad' (short for advert).
'pig' becomes 'boar' (I've seen this before).
'taken inside' means one lot of letters goes inside another.
'ad' going around 'boar' is 'ABOARD'.
(Other definitions for aboard that I've seen before include "On an aircraft" , "on gig, perhaps?" , "on a liner, say" , "On ship or plane - not on land" , "... [CRUISE SHIP] here, perhaps" .)