What would be narrower if it weren't tree-lined? (6)
I believe the answer is:
street
'what would be narrower' is the definition.
I can't judge whether this definition defines the answer.
'it weren't tree-lined?' is the wordplay.
I cannot quite understand how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is located in the answer.
an anagram of 'tree' is 'reet' which is within the answer.
A single letter 's' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
'if' is the link.
Can you help me to learn more?
(Other definitions for street that I've seen before include "Form of theatre" , "Urban thoroughfare" , "Acceptability amongst the 'with it' young" , "A thoroughfare or public road" , "Part of motorist's route" .)