Compositional etymology. In the wording of the Suda, δῆλα is an adverb, the candle "burns clearly". In the wording of the Gudianum, δῆλα (to be deduced from δηλοῖ) is probably the object. This is a nice example of etymologizing loanwords – the Greeks were probably not conscious that κανδήλη or κανδῆλα (the word is given with two different nominatives) was a loanword and they analyzed it as a Greek word. Anyway, even if they had been conscious that the word was borrowed from Latin candēla, there would be no contradiction in the principle since the theory that Latin was a derived variant of Aeolic (hence, Greek) was taken seriously by Latin grammarians.