Beam from top of roof, indeed (3)
I believe the answer is:
ray
'beam' is the definition.
(synonyms)
'top of roof indeed' is the wordplay.
'top of' indicates taking the first letters.
'indeed' becomes 'ay' ('ay' and 'aye' can mean yes).
The initial letter of 'roof' is 'r'.
'r'+'ay'='RAY'
'from' acts as a link.
(Other definitions for ray that I've seen before include "A bright beam or flat fish" , "beamer?" , "Lindwall" , "Narrow beam of light" , "Pencil of light" .)