Crossword Genius

In shadow, exercise without feeling the power in the sun? (8)

Ross

I believe the answer is:

penumbra

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

'in shadow' is the definition.
'penumbra' can be an answer for 'shadow' (I have seen 'Imperfect shadow' mean 'penumbra' so perhaps 'shadow' could also mean 'penumbra'). I'm unsure of the 'in' bit.

'exercise without feeling the power in the sun?' is the wordplay.
'exercise' becomes 'pe' (Physical Education).
'without feeling' becomes 'numb' (I've seen this before).
'the power in the sun?' becomes 'ra' (I can't explain this - if you can you should believe this answer much more).
'pe'+'numb'+'ra'='PENUMBRA'

Can you help me to learn more?

(Other definitions for penumbra that I've seen before include "Area of half shade" , "Ring around sunspot" , "Shady area" , "Imperfect shadow" , "Outer shadow round object" .)

I've seen this clue in The Times.
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