Rod and line in cart (6)
I believe the answer is:
Here is my best explanation:
'cart' is the definition.
(barrow is a kind of cart)
'rod and line' is the subsidiary indication.
'rod' becomes 'bar' (I've seen this before).
'and' is a charade indicator (letters next to each other).
'line' becomes 'row' (row is a kind of line**).
'in' is the link.
(Other definitions for barrow that I've seen before include "Small cart with two wheels, or old burial mound", "Cart; tumulus", "Burial mound; handcart", "Garden cart", "Small cart for a prehistoric burial mound", "Cart for carrying small loads", "Ancient burial mound", "Handcart; burial mound", "One-wheeled handcart" and "Small cart with two wheels for carrying things".)