Runs old companies in fine style (6)
I believe the answer is:
rococo
'fine style' is the definition.
(I've seen this before)
'runs old companies' is the wordplay.
'runs' becomes 'r' (cricket abbreviation).
'old' becomes 'o' (abbreviation).
'companies' becomes 'coco' (co for company, twice).
'r'+'o'+'coco'='ROCOCO'
'in' is the link.
(Other definitions for rococo that I've seen before include "Delicate architectural style from 18th-century France" , "Late Baroque artistic style" , "Extravagant in style" , "Ornate style of decoration." , "Florid style" .)