Very narrow lane in a hollow (6)
I believe the answer is:
valley
'a hollow' is the definition.
(I've seen this in another clue)
'very narrow lane' is the wordplay.
'very' becomes 'v' (abbreviation).
'narrow lane' becomes 'alley' (I've seen this before).
'v'+'alley'='VALLEY'
'in' acts as a link.
(Other definitions for valley that I've seen before include "Vale" , "in victory with large marble" , "See 14" , "den" , "Hollow between hills" .)