Father's not taking part in mad prank (5)
I believe the answer is:
antic
'mad prank' is the definition.
'antic' can be an answer for 'prank' (synonyms). I'm not certain of the 'mad' bit.
'father's not taking part' is the wordplay.
'father's not' becomes 'anc' (I can't justify this - if you can you should believe this answer much more).
'taking' is an insertion indicator.
'part' becomes 'ti' (ti is a kind of part).
'anc' placed around 'ti' is 'ANTIC'.
'in' is the link.
Can you help me to learn more?
(Other definitions for antic that I've seen before include "Caper; grotesque (arch.)" , "Mad act done for fun" , "old buffoon" , "Frolic" , "Tomfoolery" .)