Bug concealed after aide-de-camp deserted (5)
I believe the answer is:
aphid
'bug' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
(Other definitions for aphid that I've seen before include "Small insect like greenfly" , "Plant louse" , "Small plant-sucking insect" , "Insect feeding on plant juices" , "Garden pest" .)