Long time since deregulation for companies (8)
I believe the answer is:
agencies
'for companies' is the definition.
(agency can mean a company or organisation)
'long time since deregulation' is the wordplay.
'long time' becomes 'age' (an age is a period of time).
'deregulation' indicates an anagram.
'since' anagrammed gives 'ncies'.
'age'+'ncies'='AGENCIES'
(Other definitions for agencies that I've seen before include "Businesses that provide services on behalf of others" , "(Travel) offices" , "Businesses that serves other businesses" , "Businesses that serve others" , "Firms who transact business for others, perhaps actors" .)