A standard of soft warm-heartedness? (3)

I believe the answer is:

par

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'a standard' is the definition.
(I've seen this before)

'soft warm-heartedness?' is the wordplay.
'soft' becomes 'p' (musical abbreviation for 'piano').
'warm-heartedness?' becomes 'ar' (I can't explain this - if you can you should believe this answer much more).
'p'+'ar'='PAR'

'of' is the link.

Can you help me to learn more?

(Other definitions for par that I've seen before include "Regular score" , "Target score (golf)" , "Standard score for golfers" , "Average score for round of golf" , "Normal golfing score" .)

I've seen this clue in the Evening Standard.

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