Heard of very strange market (6)
I believe the answer is:
bazaar
'market' is the definition.
(I've seen this before)
'heard of very strange' is the wordplay.
'heard of' indicates a 'sounds like' (homophone) clue.
'very strange' becomes 'bizarre' (I've seen this before).
'bizarre' is a homophone of 'BAZAAR'.
(Other definitions for bazaar that I've seen before include "Souk" , "Parish event" , "Open-air market of oriental origin" , "exchange ..." , "Oriental market place" .)