Debts, the basis for strikebreaker in plant (8)
I believe the answer is:
scabious
'plant' is the definition.
(scabious is a kind of plant)
'debts the basis for strikebreaker' is the wordplay.
'debts' becomes 'IOUs' (promises to pay debts).
'the basis for' is a charade indicator (letters next to each other).
'strikebreaker' becomes 'scab' (synonyms).
'ious' put after 'scab' is 'SCABIOUS'.
'in' is the link.
(Other definitions for scabious that I've seen before include "Wild flower" , "Plant of the teasel family - covered in mange - so is Cuba (anag)" , "One blooming" , "Casio bus (anag) - plant" , "Bluish purple flower" .)