Got up to welcome fan before second match which made them flush (7)

'made them flush' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.

'got up to welcome fan before second match' is the wordplay.
'got up' becomes 'rose' (past tense of 'raise').
'to welcome' means one lot of letters goes inside another (in sense of 'inviting in').
'fan before' becomes 'ac' (I can't justify this - if you can you should believe this answer much more).
'second match' becomes 'a' (cnd letter of 'match').
'rose' placed around 'ac' is 'rosace'.
'rosace'+'a'='ROSACEA'

'which' is the link.

Can you help me to learn more?