Light support (4)
I believe this clue is a double definition.
'light' is the first definition.
(I know that beam is a type of light)
'support' is the second definition.
(I know that beam is a type of structural member)
(Other definitions for beam that I've seen before include "A supportive" , "Smile radiantly" , "Smile; wooden supporter?" , "Column of light" , "Smile, transmit (radio signal)" .)
'light support' is the definition.
'lamppost' can be an answer for 'support' (lamppost is a kind of support). I'm unsure of the 'light' bit.
'light support' is the wordplay.
'light' becomes 'lamp' (lamp is a kind of light).
'support' becomes 'post' (post is a kind of support).
'lamp'+'post'='LAMPPOST'
Can you help me to learn more?
(Other definitions for lamppost that I've seen before include "Street feature" , "Street light supporter" , "Support for public illumination" , "Enlightenment can be obtained from this" , "Pole, light-headed" .)