Time to invoke the Muse (5)
I believe the answer is:
erato
'the muse' is the definition.
(Erato is an example)
'time to' is the wordplay.
'time' becomes 'era' (era is a kind of time).
'era'+'to'='ERATO'
'invoke' is the link.
(Other definitions for erato that I've seen before include "Poet's muse" , "One of nine" , "Greek muse - orate (anag)" , "Muse of lyric love-poetry" , "poetical inspiration" .)