Root we'd seen in Home Counties? (5)
I believe the answer is:
swede
'root' is the definition.
(I know that swede is a type of root vegetable)
'we'd seen in home counties?' is the wordplay.
'seen in' indicates putting letters inside.
'home counties?' becomes 'SE' (Home Counties in the South East of England).
'wed' inserted into 'se' is 'SWEDE'.
(Other definitions for swede that I've seen before include "N European" , "Cattle fodder" , "Nobel for one" , "Sort of turnip - one from Scandinavia?" , "plant" .)