Beeb, lacking leader, is free (5)
I believe the answer is:
untie
'is free' is the definition.
(thesaurus)
'beeb lacking leader' is the wordplay.
'beeb' becomes 'auntie' (both are nicknames for the BBC).
'lacking leader' means to remove the first letter.
'auntie' with its initial letter taken away is 'UNTIE'.
(Other definitions for untie that I've seen before include "Remove fastenings from" , "Remove ropes, unfasten" , "get rid of bonds" , "resolve" , "Unite (anag)" .)