Presumably one gets a light tan from it (3,4)
I believe the answer is:
sun lamp
'tan from it' is the definition.
The definition suggests a singular noun which matches the answer.
'presumably one gets a light' is the wordplay.
'presumably' becomes 'sun' (I can't justify this - if you can you should give a lot more credence to this answer).
'one gets' says to put letters next to each other.
'a light' becomes 'lamp' (lamp is a kind of light).
'sun'+'lamp'='SUN-LAMP'
Can you help me to learn more?
(Other definitions for sun lamp that I've seen before include "Tanning device" , "Device for producing a tan" , "Tanner" , "UV aid to tanning" , "Bronzer?" .)