Father welcomes a time for sarcasm! (6)
I believe the answer is:
satire
'sarcasm' is the definition.
('satire' can be a synonym of 'sarcasm')
'father welcomes a time' is the wordplay.
'father' becomes 'sire' ('sire' can be a synonym of 'father').
'welcomes' means one lot of letters goes inside another (in sense of 'invites in').
'time' becomes 't'.
'a'+'t'='at'
'sire' placed around 'at' is 'SATIRE'.
'for' is the link.
(Other definitions for satire that I've seen before include "Mockery" , "Caustic comments" , "It holds up folly to ridicule" , "burlesque" , "Unkind piece of writing" .)