Harsh master apt to turn ratty about a bit of fun (6)
I believe the answer is:
tyrant
'harsh master apt' is the definition.
I can't judge whether this defines the answer.
'turn ratty about a bit of fun' is the wordplay.
'turn' is an anagram indicator.
'about' is an insertion indicator.
'a bit of fun' becomes 'n' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'ratty' with letters rearranged gives 'tyrat'.
'tyrat' going around 'n' is 'TYRANT'.
'to' acts as a link.
Can you help me to learn more?
(Other definitions for tyrant that I've seen before include "Autocrat or despot" , "bully - with 17d" , "Oppressor" , "big bully" , "Harsh and absolute ruler" .)