Keep plugging away in private, working (7,2)
I believe the answer is:
soldier on
'keep plugging away' is the definition.
I can't judge whether this definition defines the answer.
'private working' is the wordplay.
'private' becomes 'soldier' (I am not sure about this - if you are sure you should believe this answer much more).
'working' becomes 'on' (on can mean working or activated).
'soldier'+'on'='SOLDIER ON'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for soldier on that I've seen before include "Don't give up" , "plug away" , "Persevere (colloq.)" , "keep going" , "Keep struggling" .)