Delighted with a thought (6)
I believe the answer is:
amused
'delighted' is the definition.
(thesaurus)
'with a thought' is the wordplay.
'with' means one lot of letters go next to another.
'thought' becomes 'mused' (musing is a kind of thinking).
'a' put next to 'mused' is 'AMUSED'.
(Other definitions for amused that I've seen before include "Kept someone entertained" , "Provoked mirth in" , "happily occupied" , "Made (someone) laugh" , "Tickled pink" .)