Narrow opening in a northern river? This will provide more room (6)
I believe the answer is:
annexe
'this will provide more room' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'narrow opening in a northern river?' is the wordplay.
'opening' indicates taking the first letters.
'in' is an insertion indicator.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'river?' becomes 'exe' (River Exe).
The initial letter of 'narrow' is 'n'.
'a'+'n'='an'
'n' inserted into 'an' is 'ann'.
'ann'+'exe'='ANNEXE'
Can you help me to learn more?
(Other definitions for annexe that I've seen before include "Building attached to a larger one" , "Building joined to a larger one" , "extra space" , "Building attached to a largerone" , "Wing - extension" .)