Mush writer’s maverick boss is stern at heart (3,6)

I believe the answer is:

sob sister

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

'mush writer's' is the definition.
'sob sister' can be an answer for 'writer's' (sob sister is a kind of writer). I'm unsure of the 'mush' bit.

'maverick boss is stern at heart' is the wordplay.
'maverick' is an anagram indicator.
'at heart' indicates the central letters.
The middle of 'stern' is 'ter'.
'boss' anagrammed gives 'sobs'.
'sobs'+'is'+'ter'='SOB-SISTER'

Can you help me to learn more?

(Other definitions for sob sister that I've seen before include "She writes" , "Female journalist" .)

I've seen this clue in The Hindu.

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