It’s funny to be fetching diamonds for the beginning of Lent (6)
I believe the answer is:
comedy
'it's funny' is the definition.
'be fetching diamonds for the beginning of lent' is the wordplay.
I cannot quite understand how this works, but
'be' could be 'come' (coming is a kind of being) and 'come' is found within the answer.
'diamonds' could be 'd' (abbreviation in bridge say) and 'd' is present in the answer.
A single letter 'y' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
'to' is the link.
(Other definitions for comedy that I've seen before include "fun" , "Humorous film/play" , "Dante wrote ''The Divine . . . . . .''" , "Play with happy ending" , "Play with two sets of twins" .)