Everyone I must restrain runs fast (7)
I believe the answer is:
allegro
'fast' is the definition.
(similar in meaning)
'everyone i must restrain runs' is the wordplay.
'everyone' becomes 'all' (all people).
'i' becomes 'ego' ('I' in Latin).
'must restrain' means one lot of letters goes inside another.
'runs' becomes 'r' (cricket abbreviation).
'ego' placed around 'r' is 'egro'.
'all'+'egro'='ALLEGRO'
(Other definitions for allegro that I've seen before include "Quickly (in music)" , "Brisk movement or passage" , "Austin" , "Brisk musical piece" , "Scored briskly" .)