Huge birthday dinner? Do this to candles! (4-3)
I believe the answer is:
blow-out
'huge birthday dinner?' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'do this to candles' is the wordplay.
I cannot really understand how this works, but
'do' could be 'ut' ('ut' can be a synonym of 'do') and 'ut' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for blow-out that I've seen before include "Lavish meal (slang) - puncture (colloq)" , "Sudden tyre burst - large filling meal" .)