Crossword Genius

Describes unique experience alluded to by talking heads? (15)

Ross

I believe the answer is:

onceinalifetime

I'm a little stuck... Click here to teach me more about this clue!

'alluded to by talking heads?' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.

'describes unique experience' is the wordplay.
I cannot quite see how this works, but
'unique' could be 'i' and 'i' is found in the answer.
'experience' could be 'time' (time is a kind of experience) and 'time' is located in the answer.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in The Irish Times.
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