Amusing aspects will include debt (9)
I believe the answer is:
facetious
'amusing' is the definition.
'aspects will include debt' is the wordplay.
'aspects' becomes 'facets' ('facet' can be a synonym of 'aspect').
'will include' indicates putting letters inside.
'debt' becomes 'iou'.
'facets' enclosing 'iou' is 'FACETIOUS'.
(Other definitions for facetious that I've seen before include "Flippant, frivolous" , "Flippantly humorous" , "Waggish" , "Tongue-in-cheek" , "Using inapt humour" .)