Sunny little chap with a warm heart (5)

I believe the answer is:

solar

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'sunny' is the definition.
(I've seen this in another clue)

'little chap with a warm heart' is the wordplay.
'little chap' becomes 'sol' (I am not sure about the 'little' bit.).
'with' is a charade indicator (letters next to each other).
'heart' says to take the centre.
The middle of 'warm' is 'ar'.
'sol'+'ar'='SOLAR'

Can you help me to learn more?

(Other definitions for solar that I've seen before include "Using the sun's energy" , "sunny?" , "Pertaining to the sun" , "revolutionary system" , "Using the energy of the sun" .)

I've seen this clue in the Evening Standard.

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