Strip smashed under ship (7)
I believe the answer is:
undress
'strip' is the definition.
(synonyms)
'smashed under ship' is the wordplay.
'smashed' indicates an anagram.
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'under' with letters rearranged gives 'undre'.
'undre'+'ss'='UNDRESS'
(Other definitions for undress that I've seen before include "Disrobe - uniform for ordinary occasions" , "Remove clothes, strip" , "Take off clothing, strip" , "Sunders (anag)" , "Strip, take off clothes" .)