Cheer if returning new synthetic fibre (6)

I believe the answer is:

olefin

I'm a little stuck... Click here to teach me more about this clue!

'synthetic fibre' is the definition.
The definition suggests a singular noun which matches the answer.

'cheer if returning new' is the wordplay.
'cheer' becomes 'ole' (I've seen this in another clue).
'returning' shows that the letters should be reversed in order.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'if' written backwards gives 'fi'.
'ole'+'fi'+'n'='OLEFIN'

Can you help me to learn more?

(Other definitions for olefin that I've seen before include "Unsaturated hydrocarbon; no life (anag.)" , "Type of hydrocarbon; no life (anagram)" , "ethylene exemplifies" , "Hydrocarbon like ethylene; on file (anag.)" , "compound" .)

I've seen this clue in the Sydney Morning Herald.

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