Good Lord concerned with former associate (9)
I believe the answer is:
correlate
'associate' is the definition.
(I know that correlate is a more specific form of the action associate)
'good lord concerned with former' is the wordplay.
'good lord' becomes 'cor' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'concerned with' becomes 're' (re can mean regarding or about).
'former' becomes 'late' (late can mean former or previous).
'cor'+'re'+'late'='CORRELATE'
Can you help me to learn more?
(Other definitions for correlate that I've seen before include "Make a connection between (things)" , "Match" , "Bring (things) into correspondence" , "(Of two things) tally" , "Establish a mutual relationship between (things)" .)