Explosive device initially excited fool (7)
I believe the answer is:
deceive
'fool' is the definition.
(thesaurus)
'explosive device initially excited' is the wordplay.
'explosive' indicates anagramming the letters.
'initially' indicates taking the first letters.
The first letter of 'excited' is 'e'.
'device' anagrammed gives 'deceiv'.
'deceiv'+'e'='DECEIVE'
(Other definitions for deceive that I've seen before include "Mislead, delude" , "Hoodwink" , "Cheat or mislead" , "Intentionally mislead" , "Give a wrong impression to" .)