At Gateshead, the forest is of horticultural interest (6)
I believe the answer is:
garden
'of horticultural interest' is the definition.
The definition suggests a singular noun which matches the answer.
'at gateshead the forest' is the wordplay.
'at' says to put letters next to each other.
'gateshead' becomes 'g' (head letter of 'gates').
'the forest' becomes 'arden' (forest in Shakespeare's As You Like It).
'g' next to 'arden' is 'GARDEN'.
'is' is the link.
Can you help me to learn more?
(Other definitions for garden that I've seen before include "Area for growing plants" , "Where, eg, flowers are grown" , "-- City; -- centre" , "Plant growing area" , "Domestic plot" .)