In simple terms, leased (3)
I believe the answer is:
let
'leased' is the definition.
(thesaurus)
'in simple terms' is the wordplay.
'in' says the answer is hidden in the clue.
'LET' is hidden within 'simple terms'.
(Other definitions for let that I've seen before include "Allow; rental period" , "& 15 Triple (anag.)" , "Allow; leased" , "Won't stop you" , "hired" .)