A bad-tempered pet (7)
I believe the answer is:
tantrum
'pet' is the definition.
(I've seen this before)
'a bad-tempered' is the wordplay.
I cannot quite see how this works, but
'a' could be 'an' and 'an' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for tantrum that I've seen before include "Paddy" , "Uncontrolled outburst of anger" , "Spoilt brat's fit" , "Fit - pet" , "Hissy fit" .)