Picked up inflatable mattress to go into hiding (3,3)
I believe the answer is:
lie low
'go into hiding' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for lie low that I've seen before include "Keep concealed or quiet" , "Stay out of sight, be inconspicuous" , "don't show your face" , "Go into hiding" , "Avoid attracting notice" .)