Welly-boot we regularly found in barge (5)
I believe the answer is:
elbow
'barge' is the definition.
(I've seen this before)
'welly-boot we regularly' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'welly'+'boot'+'we'='wellybootwe'
The alternating letters of 'wellybootwe' are 'ELBOW'.
'found in' acts as a link.
(Other definitions for elbow that I've seen before include "part of the body" , "given to one about to leave" , "Sort of grease" , "Reject" , "Hinge joint" .)