Single regulation first person had raised referred to festival of lights (6)
I believe the answer is:
diwali
'to festival of lights' is the definition.
(I've seen this before)
'single regulation first person had raised' is the wordplay.
'single' becomes 'I' (one).
'regulation' becomes 'law' (I've seen this before).
'first person' becomes 'I' (first-person pronoun).
'had' becomes 'd' (in contractions e.g. 'I'd', 'you'd' etc).
'raised' says the letters should be written in reverse (going up in a down clue).
'i'+'law'+'i'+'d'='ilawid'
'ilawid' back-to-front is 'DIWALI'.
'referred' acts as a link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for diwali that I've seen before include "Indian festival" , "religious festival" , "Hindu festival; I'd wail (anag.)" , "Festival in honour of Lakshmi" , "Light festival" .)