Guardian's role initially, advocating ten essential glute exercises (8)
I believe the answer is:
tutelage
'guardian's role' is the definition.
'initially advocating ten essential glute exercises' is the wordplay.
'initially' says to take the initial letters.
'exercises' is an anagram indicator (I've seen 'exercised' mean this).
The first letters of 'advocating ten essential' is 'ate'.
'ate'+'glute'='ateglute'
'ateglute' with letters rearranged gives 'TUTELAGE'.
(Other definitions for tutelage that I've seen before include "Guardianship; instruction" , "Instruction by personal teacher" , "Schooling" , "guidance" , "Tuition" .)