'Telegraph' work -- it involved high-level performer (9,6)
I believe the answer is:
tightrope walker
'high-level performer' is the definition.
(someone who performs high up in the air)
'telegraph work it involved' is the wordplay.
'involved' is an anagram indicator (involved can mean confusing or complex).
'telegraph'+'work'+'it'='telegraphworkit'
'telegraphworkit' with letters rearranged gives 'TIGHTROPE WALKER'.
(Other definitions for tightrope walker that I've seen before include "Charles Blondin, perhaps" , "Funambulist'" , "As one taking highly risky steps" , "Circus performer" , "circus act" .)