Regale a source of inspiration (5)
I believe the answer is:
amuse
'regale' is the definition.
(I've seen this in another clue)
'a source of inspiration' is the wordplay.
'source of inspiration' becomes 'muse' (I've seen this in another clue).
'a'+'muse'='AMUSE'
(Other definitions for amuse that I've seen before include "Keep occupied" , "Cause mirth - distract" , "Recreate" , "Cause to laugh or smile" , "Make (someone) laugh" .)