Father returned and concealed bug (5)
I believe the answer is:
aphid
'bug' is the definition.
(type of insect)
'father returned and concealed' is the wordplay.
'father' becomes 'pa' (pa can mean dad or father).
'returned' says the letters should be written in reverse.
'and' is a charade indicator (letters next to each other).
'concealed' becomes 'hid' ('hide' can be a synonym of 'conceal').
'pa' in reverse letter order is 'ap'.
'ap'+'hid'='APHID'
(Other definitions for aphid that I've seen before include "plant pest" , "Sap-sucking bug" , "Horticultural pest" , "Blackfly or greenfly" , "Small plant-sucking insect" .)