Gap traversed by the German fishing-boat (7)
I believe the answer is:
drifter
'fishing-boat' is the definition.
(I've seen this before)
'gap traversed by the german' is the wordplay.
'gap' becomes 'rift' (rift is a kind of gap).
'traversed by' is an insertion indicator.
'the german' becomes 'der' ('the' in German).
'rift' going inside 'der' is 'DRIFTER'.
(Other definitions for drifter that I've seen before include "Fishing boat; nomad" , "Itinerant type" , "Ship - a tramp, possibly" , "One who moves about aimlessly" , "Bum" .)