Right to swap tops before tramp visits Lord - his job is on the line (9,6)
I believe the answer is:
tightrope walker
'his job is on the line' is the definition.
(someone who walks in a line along a tightrope)
'right to swap tops before tramp visits lord' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'right' is 'ightr' which is within the answer.
'to' is within the answer.
This may be the basis of clue (or it may be nonsense).
(Other definitions for tightrope walker that I've seen before include "Charles Blondin, perhaps" , "circus act" , "Circus performer" , "Funambulist'" , "As one taking highly risky steps" .)