Building close to New Forest is one used for smoking (12)
I believe the answer is:
churchwarden
'one used for smoking' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'building close to new forest' is the wordplay.
'building' becomes 'church' (church is a kind of building).
'close to' indicates one should take the final letters (the 'close' to the word).
'forest' becomes 'arden' (Forest of Arden).
The final letter of 'new' is 'w'.
'church'+'w'+'arden'='CHURCHWARDEN'
'is' is the link.
Can you help me to learn more?
(Other definitions for churchwarden that I've seen before include "Long clay pipe" , "Parish officer - long-stemmed pipe" , "one seen to smoke" , "Long-stemmed clay pipe; parish representative" .)