Frame of mind reversed the lot (4)

I believe the answer is:

mood

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'frame of mind' is the definition.
(I've seen this in another clue)

'reversed the lot' is the wordplay.
'reversed' becomes 'moo' (I can't justify this - if you can you should give a lot more credence to this answer).
'the lot' becomes 'd'.
'moo'+'d'='MOOD'

Can you help me to learn more?

(Other definitions for mood that I've seen before include "State of mind, humour" , "Humour - bad temper" , "An atmosphere of doom" , "melancholy" , "Depression" .)

I've seen this clue in the Sydney Morning Herald.

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