Very unfortunate time, with export from Cuba brought back (6)
I believe the answer is:
tragic
'very unfortunate' is the definition.
(tragic can mean terrible or unfortunate)
'time with export from cuba brought back' is the wordplay.
'time' becomes 't' (abbreviation).
'with' says to put letters next to each other.
'export from cuba' becomes 'cigar' (Cuba famously exports cigars).
'brought back' says the letters should be written backwards.
'cigar' written backwards gives 'ragic'.
't'+'ragic'='TRAGIC'
(Other definitions for tragic that I've seen before include "Disastrous, desperately sad" , "Extremely sad; Mahler's 6th nickname" , "Dreadful" , "like King Lear" , "Exceedingly sad" .)