Display behind Low cartoon, at the back (4)
I believe the answer is:
moon
'display' is the definition.
(mooning is a kind of displaying)
'behind low cartoon at the back' is the wordplay.
'behind' says to put letters next to each other.
'low' becomes 'moo' (both can mean to make the noise of a cow).
'at the back' says to take the final letters.
The last letter of 'cartoon' is 'n'.
'moo'+'n' is 'MOON'.
(Other definitions for moon that I've seen before include "Night light" , "Shining ball of green cheese?" , "Where Armstrong stood" , "Reveal rear" , "Idle (around) - satellite" .)