This is a charade - two separate parts of the clue each contribute a portion of the answer, which are then joined together.
'Wingless' is the key modifier. Take a word meaning 'lustrous' and remove its 'wings' (outer letters) to get the first part. The second part comes from another reading of 'bug' as a verb.
Answer: LISTEN IN | 'Lustrous' = GLISTEN, remove wings (outer letters G and N) = LISTEN. 'Bug' as a verb means to eavesdrop = IN. LISTEN + IN = LISTEN IN (to eavesdrop).