After long time at new company, got discontented with office (6)
I believe the answer is:
agency
'office' is the definition.
(synonyms)
'after long time at new company' is the wordplay.
'after' says to put letters next to each other.
'long time' becomes 'age' (synonyms).
'at' means one lot of letters go next to another.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'company' becomes 'cy' (I can't explain this - if you can you should give a lot more credence to this answer).
'n' next to 'cy' is 'ncy'.
'age' put next to 'ncy' is 'AGENCY'.
'got discontented with' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for agency that I've seen before include "Intervention producing a particular effect" , "Government office" , "Business that represents actors etc." , "Organisation providing a particular service" , "Means - business" .)