Drawing of small boat (6)
I believe the answer is:
sketch
'drawing' is the definition.
(I know that sketch is a type of drawing)
'small boat' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'boat' becomes 'ketch' (ketch is a type of sailing boat).
's'+'ketch'='SKETCH'
'of' is the link.
(Other definitions for sketch that I've seen before include "Rough picture" , "bit of a performance" , "Rough outline" , "'A rough, quick drawing (6)'" , "Short dramatic scene" .)