Source of inspiration (4)
I believe the answer is:
muse
'source of inspiration' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for muse that I've seen before include "Source of inspiration; rock group" , "Be absorbed in thought" , "Ponder, say meditatively" , "Contemplate -- a goddess of the liberal arts" , "Ponder in meditative way" .)