Zealous umpire turns to give out (7)

I believe the answer is:

fervent

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'zealous' is the definition.
(I've seen this before)

'umpire turns to give out' is the wordplay.
'umpire' becomes 'ref' (I've seen this before).
'turns' says the letters should be written in reverse.
'to give out' becomes 'vent' (I can't justify this - if you can you should believe this answer much more).
'ref' written backwards gives 'fer'.
'fer'+'vent'='FERVENT'

Can you help me to learn more?

(Other definitions for fervent that I've seen before include "Ardent" , "Zealous" , "Intensely passionate" , "Impassioned" , "Enthusiastic" .)

I've seen this clue in The Sun.

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