Small boat in rough drawing (6)
I believe the answer is:
sketch
'rough drawing' is the definition.
(I've seen this in another clue)
'small boat' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'boat' becomes 'ketch' (ketch is a kind of sailing vessel).
's'+'ketch'='SKETCH'
'in' is the link.
(Other definitions for sketch that I've seen before include "Short humorous scene" , "'A rough, quick drawing (6)'" , "Outline - preliminary drawing" , "Delineate" , "bit of a performance" .)