Maybe panto backer's high spirits? (6)
I believe the answer is:
angels
'maybe panto' is the definition.
I can't tell whether this definition defines the answer.
'backer's high spirits?' is the wordplay.
'backer' becomes 'angel' (an angel is a financial backer).
'high' suggests taking the first letters (I've seen 'highest of' mean this (top letter - down clues only)).
The initial letter of 'spirits' is 's'.
'angel'+'s'='ANGELS'
Can you help me to learn more?
(Other definitions for angels that I've seen before include "Theatrical investors" , "Supernatural messengers" , "Gleans that they're heavenly" , "See 9" , "See 13" .)