Speak of a zero charge (5)

I believe the answer is:

orate

'speak' is the definition.
(I know that orate is a type of speak)

'a zero charge' is the wordplay.
'a zero' becomes 'O' (O resembles 0).
'charge' becomes 'rate' (rate is a kind of charge).
'o'+'rate'='ORATE'

'of' is the link.

(Other definitions for orate that I've seen before include "Speechify" , "Speak in public" , "Speak pompously and at length" , "Speak publicly" , "Hold forth" .)

I've seen this clue in the Evening Standard.

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