Lights out et al (5)
I believe the answer is:
offal
'lights' is the definition.
(I've seen this before)
'out et al' is the wordplay.
I cannot really see how this works, but
'out' could be 'off' (I've seen this before) and 'off' is located in the answer.
'al' is present in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for offal that I've seen before include "cheap meat" , "Edible heart, liver and tongue, for instance" , "Edible internal parts" , "Edible insides" , "Animal entrails and internal organs as rubbish" .)