With respect to problem marriage, finally continue (6)
I believe the answer is:
resume
'continue' is the definition.
(resuming is a kind of continuing)
'with respect to problem marriage finally' is the wordplay.
'with respect to' becomes 're' (I've seen this in other clues).
'problem' becomes 'sum' (arithmetic problem).
'finally' says to take the final letters.
The final letter of 'marriage' is 'e'.
're'+'sum'+'e'='RESUME'
(Other definitions for resume that I've seen before include "Start again where one left off" , "Begin the summary again?" , "Speak again" , "Start again having taken a break" , "Continue after pause" .)