Notice mate mirroring devices (7)
I believe the answer is:
laptops
'devices' is the definition.
(laptop is a kind of device)
'notice mate mirroring' is the wordplay.
'notice' becomes 'spot' (spot can mean to notice or observe).
'mate' becomes 'pal' (I've seen this before).
'mirroring' is a reversal indicator (I've seen 'mirrored' mean this).
'spot'+'pal'='spotpal'
'spotpal' written backwards gives 'LAPTOPS'.
(Other definitions for laptops that I've seen before include "PCs" , "more than one PC" , "Portable computers" .)