Allow George at first to sound off (5)
I believe the answer is:
grant
'allow' is the definition.
(I know that allow can be written as grant)
'george at first to sound off' is the wordplay.
'at first' suggests taking the first letters.
'to sound off' becomes 'rant' (to sound off is to rant or complain).
The first letter of 'george' is 'g'.
'g'+'rant'='GRANT'
(Other definitions for grant that I've seen before include "Cary, Duncan or Ulysses S?" , "Give or allow as a privilege" , "Greek, a soldier" , "Give freely" , "Give (a right); gift" .)