Herbal remedy: always fine with small quantity about (8)
I believe the answer is:
feverfew
'herbal remedy' is the definition.
(feverfew is used as a herbal remedy)
'always fine with small quantity about' is the wordplay.
'always' becomes 'ever' (synonyms).
'fine' becomes 'f' (abbreviation).
'with' means one lot of letters go next to another.
'small quantity' becomes 'few' (I've seen this in another clue).
'about' is an insertion indicator.
'ever'+'f'='everf'
'everf' put inside 'few' is 'FEVERFEW'.
(Another definition for feverfew that I've seen is " Medicinal plant".)