Male relatives at start of donkey race (7)
I believe the answer is:
mankind
'race' is the definition.
(I've seen this before)
'male relatives at start of donkey' is the wordplay.
'male' becomes 'man' (man is a kind of male).
'relatives' becomes 'kin' (kin can mean relatives or family).
'at start of' says to take the initial letters.
The first letter of 'donkey' is 'd'.
'man'+'kin'+'d'='MANKIND'
(Other definitions for mankind that I've seen before include "Human race" , "Humanity" , "people, in general" , "People generally" , "'One giant leap for - - '" .)