Praise what used to be a lot different (5)

I believe the answer is:

extol

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'praise' is the definition.
(I know that extol is a more specific form of the action praise)

'used to be a lot different' is the wordplay.
'used to be' becomes 'ex' (I can't justify this - if you can you should give a lot more credence to this answer).
'different' indicates anagramming the letters (letters placed in a different order).
'lot' with letters rearranged gives 'tol'.
'ex'+'tol'='EXTOL'

'what' acts as a link.

Can you help me to learn more?

(Other definitions for extol that I've seen before include "Acclaim" , "celebrate" , "Speak well of" , "Praise - honour" , "Crack up" .)

I've seen this clue in the Evening Standard.

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