Retroaction occasionally one to inspire (5)

I believe the answer is:

erato

'one to inspire' is the definition.
(one of the Greek muses)

'retroaction occasionally' is the wordplay.
'occasionally' means one should take alternating letters.
The alternating letters of 'retroaction' are 'ERATO'.

(Other definitions for erato that I've seen before include "Muse of 11 and 23" , "inspiration for poetry" , "Muse of lyric love-poetry" , "One of nine" , "Source of poetic inspiration" .)

I've seen this clue in The Independent.

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