Favourite Disney film losing millions? Start to turn peevish (8)
I believe the answer is:
petulant
'peevish' is the definition.
(synonyms)
'favourite disney film losing millions? start to' is the wordplay.
'favourite' becomes 'pet' (synonyms).
'disney film' becomes 'Mulan' (Mulan is a Disney film).
'losing' suggests deleting specific letters.
'millions?' becomes 'm' (abbreviation).
'start to' becomes 't' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'mulan' with 'm' removed is 'ulan'.
'pet'+'ulan'+'t'='PETULANT'
'turn' acts as a link.
This may not be right. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for petulant that I've seen before include "Fractious, pouty" , "Querulous and demanding" , "Easily irritated" , "Childishly sulky or bad-tempered" , "Sullen in a peevish way" .)