Chance hurried complete with header from midfielder (6)
I believe the answer is:
random
'chance' is the definition.
(similar in meaning)
'hurried complete with header from midfielder' is the wordplay.
'hurried' becomes 'ran' (running is a kind of hurrying).
'complete' becomes 'do' (doing is a kind of completing).
'with' is a charade indicator (letters next to each other).
'header from' suggests taking the first letters.
The first letter of 'midfielder' is 'm'.
'ran'+'do'+'m'='RANDOM'
(Other definitions for random that I've seen before include "Without a particular aim, haphazard as choice may be" , "Haphazard, with no particular plan" , "Governed by chance" , "Following no method" , "Sporadic" .)