Company marks appointment that will stimulate growth (7)
I believe the answer is:
compost
'that will stimulate growth' is the definition.
'company marks appointment' is the wordplay.
'company' becomes 'co' (abbreviation).
'marks' becomes 'm' (former German currency).
'appointment' becomes 'post' (I've seen this before).
'co'+'m'+'post'='COMPOST'
(Other definitions for compost that I've seen before include "Fertiliser, maybe home-made" , "Mixture for garden" , "Growing medium" , "Manure of soil and other ingredients" , "Decaying vegetation as fertilizer" .)