Work found in sea transport (5)
I believe the answer is:
moped
'transport' is the definition.
(moped is a kind of transport)
'work found in sea' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'found in' indicates putting letters inside.
'sea' becomes 'med' (abbreviation of Mediterranean**).
'op' placed inside 'med' is 'MOPED'.
(Other definitions for moped that I've seen before include "Vehicle - was blue" , "means of transport" , "Wandered about listlessly" , "Sulked - form of transport" , "Motorised bicycle" .)