Girl student that is seen around a ship (6)
I believe the answer is:
lassie
'girl' is the definition.
(lassie is a kind of girl)
'student that is seen around a ship' is the wordplay.
'student' becomes 'l' (as in L-plates for learner drivers).
'that is' becomes 'ie' ('i.e.' can be a synonym of 'that is').
'seen around' is an insertion indicator.
'ship' becomes 'ss'.
'l'+'ie'='lie'
'a'+'ss'='ass'
'lie' going around 'ass' is 'LASSIE'.
(Other definitions for lassie that I've seen before include "Girl from Scotland and dog from film" , "Hollywood film-star dog" , "girl found" , "''Will ye go ..., go'' (folksong)" , "Scottish girl - canine movie star" .)