Father occasionally gets pissed as a newt (3)
I believe the answer is:
eft
'newt' is the definition.
(eft is a kind of newt)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for eft that I've seen before include "Little creature" , "Kind of newt found in clefts" , "Juvenile twenty-three Ac; rhymes with sinister" , "Slimy creature" , "Newt (archaic)" .)