Chesterfield, for example, third in Derbyshire until now
I believe the answer is:
sofar
'until now' is the definition.
(I've seen this before)
'chesterfield for example third in derbyshire' is the wordplay.
'chesterfield for example' becomes 'sofa' (chesterfield is a kind of sofa).
'third in derbyshire' becomes 'r' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'sofa'+'r'='SOFAR'
Can you help me to learn more?
(Other definitions for sofar that I've seen before include "To this point" , "Up till now" , "'Up to this time (2,3)'" , "'Heretofore (2,3)'" , "Up until the present moment" .)