Radio operator (3)
I believe the answer is:
ham
'radio operator' is the definition.
(as in ham radio)
This is the entire clue.
(Other definitions for ham that I've seen before include "Poor person acting" , "Thespian who overacts, informally" , "Noah's second son - a bad actor?" , "under twenty-eight [HIP]" , "Meat from a pig" .)