Stickler in bad mood about Bible book (6)
I believe the answer is:
pedant
'stickler' is the definition.
(I've seen this in another clue)
'bad mood about bible book' is the wordplay.
'bad mood' becomes 'pet' (informal term for sulking).
'about' means one lot of letters goes inside another.
'bible book' becomes 'dan' (I can't explain this - if you can you should believe this answer much more).
'pet' going around 'dan' is 'PEDANT'.
'in' is the link.
Can you help me to learn more?
(Other definitions for pedant that I've seen before include "Panted like dogmatist" , "One who insists on minor details, may be a conceited know-all" , "Pentad (anag.)" , "Know-all who insists on strict observance of rules" , "One concerned with excessive detail" .)