Line up drunk engineers to cover work (9)
I believe the answer is:
tightrope
'line up' is the definition.
(line that's up in the air)
'drunk engineers to cover work' is the wordplay.
'drunk' becomes 'tight' (slang term).
'engineers' becomes 're' (abbreviation for Royal Engineers).
'to cover' indicates putting letters inside.
'work' becomes 'op' (abbreviation for opus).
're' enclosing 'op' is 'rope'.
'tight'+'rope'='TIGHTROPE'
(Other definitions for tightrope that I've seen before include "On which acrobats walk" , "An acrobat walks on this high above the ground" , "Acrobat's walkway" , "High wire" , "Acrobats perform on it, usually with safety net" .)