Six in hiding in city environs (8)
I believe the answer is:
vicinity
'environs' is the definition.
(I've seen this before)
'six in hiding in city' is the wordplay.
'six' becomes 'VI' (Roman numerals).
'hiding in' is an insertion indicator.
'in' put within 'city' is 'cinity'.
'vi'+'cinity'='VICINITY'
(Other definitions for vicinity that I've seen before include "Nearby area" , "Surrounding or nearby region" , "environs" , "Neighbourhood" , "Surroundings" .)