Splendid monetary principal (7)
I believe the answer is:
capital
I believe this is a triple definition!
'splendid' is the first definition.
(I've seen this before)
'monetary' is the second definition.
(thesaurus)
'principal' is the third definition.
(I've seen this before)
(Other definitions for capital that I've seen before include "It's jolly good in the great city" , "Kabul or Harare?" , "Chief; excellent" , "Money available to produce interest" , "What starts this clue" .)