Fiance follows sister accepting work that isn't supposed to amuse (2,3,8)
I believe the answer is:
no pun intended
'isn't supposed to amuse' is the definition.
I can't judge whether this defines the answer.
'fiance follows sister accepting work' is the wordplay.
'fiance' becomes 'intended' (someone's intended is their fiance).
'follows' says to put letters next to each other.
'sister' becomes 'nun' (sister is a term of address for a nun).
'accepting' indicates putting letters inside (inserted letters are accepted).
'work' becomes 'op' (common abbreviation for 'opus').
'nun' placed around 'op' is 'nopun'.
'intended' put after 'nopun' is 'NO PUN INTENDED'.
'that' is the link.
Can you help me to learn more?
(Another definition for no pun intended that I've seen is " That's no joke".)