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Effect of cool current catchword I'll only half finish off (4-5,6)

Ross

I believe the answer is:

wind-chill factor

'effect of cool current' is the definition.
(weather phenomenon)

'catchword i'll only half finish off' is the wordplay.
'only half' indicates taking half.
'off' is an anagram indicator.
'finish' cut in half is 'fin'.
'catchword'+'ill'+'fin'='catchwordillfin'
'catchwordillfin' is an anagram of 'WIND-CHILL FACTOR'.

I've seen this clue in The Times.
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