Blooming half-cut Reed is unconventional (5)
I believe the answer is:
outre
'unconventional' is the definition.
(similar in meaning)
'blooming half-cut reed' is the wordplay.
'blooming' becomes 'out' (plants which have bloomed are 'out').
'half cut' means to take half the letters.
'reed' with half the letters taken is 're'.
'out'+'re'='OUTRE'
'is' is the link.
(Other definitions for outre that I've seen before include "Bizarre or eccentric in France" , "Deviating from normal" , "Freakish" , "Strange" , "Weird" .)