Support my clue Angel oddly rejected for 'flammable gas' (9)

'gas' is the definition.
(I know that propylene is a type of gas)

'support my clue angel oddly rejected' is the wordplay.
'support' becomes 'prop' (prop up can mean to support).
'oddly rejected' means one should take alternating letters (letters in odd-numbered positions removed).
'my'+'clue'+'angel'='myclueangel'
The alternate letters of 'myclueangel' are 'ylene'.
'prop'+'ylene'='PROPYLENE'

'for flammable' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.

Can you help me to learn more?