For each experience within (3)
I believe the answer is:
per
'for each' is the definition.
(thesaurus)
'experience within' is the wordplay.
'within' indicates a hidden word.
'PER' can be found hidden inside 'experience'.
(Other definitions for per that I've seen before include "For each or every" , "According to" , "Preposition indicating by means of" , "Preposition meaning for each" .)