Go to ground, unhappy after deception (3,3)
I believe the answer is:
lie low
'go to ground' is the definition.
(I've seen this before)
'unhappy after deception' is the wordplay.
'unhappy' becomes 'low'.
'after' says to put letters next to each other.
'deception' becomes 'lie' (lying to someone is deceiving them).
'low' after 'lie' is 'LIE LOW'.
(Other definitions for lie low that I've seen before include "Stay out of sight, hide horizontally?" , "avoid detection" , "Go to ground" , "Use bottom bunk, perhaps" , "take cover" .)