Phase one neglected in prehistoric period (5)

I believe the answer is:

stage

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

This clue might be a double definition.

'phase' is the first definition.
(I know that phase can be written as stage)

'one neglected in prehistoric period' is the second definition.
'stage' can be an answer for 'period' (e.g. a stage in history). I'm not sure about the 'one neglected in prehistoric' bit.

Can you help me to learn more?

(Other definitions for stage that I've seen before include "Form of transport" , "division" , "Acting platform; coach" , "Support for acting" , "Leg; part of theatre" .)

I've seen this clue in The Guardian.

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