There's always hardly any after fine plant (8)

'plant' is the definition.
(feverfew is a kind of plant)

'there's always hardly any after fine' is the wordplay.
'there's' is a charade indicator (letters next to each other).
'always' becomes 'ever' ('ever' can be a synonym of 'always').
'hardly any' becomes 'few' ('few' can be similar in meaning to 'hardly any').
'after' is a charade indicator (letters next to each other).
'fine' becomes 'f' (abbreviation).
'ever' put next to 'few' is 'everfew'.
'everfew' put after 'f' is 'FEVERFEW'.