See contrary star react, occasionally, citing proof of qualification (4)
I believe the answer is:
cert
'citing proof of qualification' is the definition.
I can't judge whether this defines the answer.
'see contrary star react occasionally' is the wordplay.
'see contrary' is a reversal indicator.
'occasionally' indicates alternate letters (letters taken at regular intervals or occasions).
'star'+'react'='starreact'
The alternating letters of 'starreact' are 'trec'.
'trec' reversed gives 'CERT'.
Can you help me to learn more?
(Other definitions for cert that I've seen before include "Inevitable event" , "Sure thing, in short" , "One sure to win (slang)" , "Banker" , "Safe bet" .)