Want a source of light, becoming angry (7)
I believe the answer is:
needled
'angry' is the definition.
(I've seen this before)
'want a source of light' is the wordplay.
'want' becomes 'need' (synonyms).
'a source of light' becomes 'led' (abbreviation for light emitting diode).
'need'+'led'='NEEDLED'
'becoming' acts as a link.
(Other definitions for needled that I've seen before include "Goaded or provoked" , "Annoyed - provoked" , "Provoked with sewing implement" , "Irritated (sl.)" , "was annoying" .)