English Premier League initially breaks constitution (6)
I believe the answer is:
health
'constitution' is the definition.
(I've seen this before)
'english premier league initially breaks' is the wordplay.
'english premier' becomes 'Heath' (Edward Heath, former UK prime minister or premier).
'initially' indicates taking the first letters.
'breaks' indicates putting letters inside (inserted letters break into the word).
The initial letter of 'league' is 'l'.
'heath' placed around 'l' is 'HEALTH'.
(Other definitions for health that I've seen before include "State of well-being" , "General condition of body (and/or mind)" , "Physical welfare" , "Fine condition" , "10 18's great creation" .)