Expert attending live investigation (5)
I believe the answer is:
probe
'investigation' is the definition.
(probe can mean an investigation or inquiry)
'expert attending live' is the wordplay.
'expert' becomes 'pro' (short for professional).
'attending' means one lot of letters go next to another.
'live' becomes 'be' (synonyms).
'pro'+'be'='PROBE'
(Other definitions for probe that I've seen before include "Spacecraft; investigation" , "Question or examine thoroughly" , "Inquiry" , "Explore, examine" , "sound" .)