Small fruit on small vessels (5)
I believe the answer is:
ships
'vessels' is the definition.
(ship is a kind of vessel)
'small fruit on small' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'fruit' becomes 'hip' (I've seen this in other clues**).
'on' says to put letters next to each other.
'small' becomes 's' (abbreviation - e.g. clothes size).
's'+'hip'+'s'='SHIPS'
(Other definitions for ships that I've seen before include "Large boats" , "Sea vessels" , "Maritime transport" .)