Physical exercises right for each (3)
I believe the answer is:
per
'each' is the definition.
(thesaurus)
'physical exercises right' is the wordplay.
'physical exercises' becomes 'pe' (physical education).
'right' becomes 'r' (common abbreviation).
'pe'+'r'='PER'
'for' is the link.
(Other definitions for per that I've seen before include "Preposition indicating by means of" , "According to" , "Preposition meaning for each" , "For each or every" .)