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