Note form of light that's covered in decoration (5)
I believe the answer is:
tiled
'covered in decoration' is the definition.
'tiled' can be an answer for 'covered' (tiling is a kind of covering). I am unsure of the 'in decoration' bit.
'note form of light' is the wordplay.
'note' becomes 'ti' (musical note, as in do re mi so fa la ti do).
'form of light' becomes 'LED' (light-emitting diode).
'ti'+'led'='TILED'
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for tiled that I've seen before include "Lined with small glazed rectangles, say bathroom" , "Covered in pottery slabs" , "Like many roofs" , "covered bathroom wall?" , "Covered the roof" .)