Extremely rare coin seen not long ago (6)
I believe the answer is:
recent
'not long ago' is the definition.
(recent means a short time ago)
'extremely rare coin' is the wordplay.
'extremely' suggests removing the centre (letters on the extremes of the word are used).
'coin' becomes 'cent' (cent is a kind of coin).
'rare' with its middle removed is 're'.
're'+'cent'='RECENT'
'seen' acts as a link.
(Other definitions for recent that I've seen before include "Happening lately" , "Occurring not long ago" , "Having been done lately" , "Fresh - current" , "Not long ago, just a little while past" .)