No source of stomach upsets in Somerset town? That’ll make you merry (10)

I believe the answer is:

frolicsome

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'merry' is the definition.
(thesaurus)

'no source of stomach upsets in somerset town?' is the wordplay.
'no' becomes 'O' (O resembles 0).
'source of stomach upsets' becomes 'lics' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in' is an insertion indicator.
'somerset town?' becomes 'frome' (I've seen this before).
'o'+'lics'='olics'
'olics' put inside 'frome' is 'FROLICSOME'.

'that'll make you' acts as a link.

Can you help me to learn more?

(Other definitions for frolicsome that I've seen before include "Lively, playful" , "Enjoying a prank" .)

I've seen this clue in The Independent.

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