Central London area, extremely fashionable almost (4)
I believe the answer is:
soho
'central london area' is the definition.
(Soho is an area of Central London)
'extremely fashionable almost' is the wordplay.
'extremely' becomes 'so' ('so' can mean 'extremely' or 'very').
'fashionable' becomes 'hot' (hot can mean fashionable or trendy).
'almost' means to remove the last letter (most of the word but not all of it).
'hot' with its last letter taken away is 'ho'.
'so'+'ho'='SOHO'
(Other definitions for soho that I've seen before include "Central London night life district" , "capital district" , "London's nightlife centre" , "District of London, noted for restaurants and nightclubs" , "London's former Bohemia" .)