Dessert is hot, left on end of tray ill-advisedly (9)

'ill-advisedly' is the definition.
Both the definition and answer are adverbs.
Maybe you can see an association between them that I don't see?

'dessert is hot left on end of tray' is the wordplay.
'dessert' becomes 'fool' (type of dessert).
'hot left' becomes 'hl' (this might be a standard abbreviation which I don't know about).
'on' says to put letters next to each other.
'end of' indicates one should take the final letters.
The final letter of 'tray' is 'y'.
'fool'+'is'+'hl'+'y'='FOOLISHLY'

Can you help me to learn more?