Carry on a trade in Plymouth (3)
I believe the answer is:
ply
This might be a double definition.
'carry' is the first definition.
(I know that carry is a is a more specific form of the action nourish)
'trade in plymouth' is the second definition.
'ply' can be an answer for 'trade' (to ply a trade is to work at it). I'm not sure about the 'in plymouth' bit.
'on a' acts as a link.
Can you help me to learn more?
(Other definitions for ply that I've seen before include "Practise (a trade)" , "This wood is laminated" , "'Persist in offering, liquor say (3)'" , "Work steadily at, say trade" , "drama one's missed" .)