Work ethic came between father and friend in passing (15)
I believe the answer is:
parenthetically
'in passing' is the definition.
(thesaurus)
'work ethic came between father and friend' is the wordplay.
I cannot quite see how this works, but
an anagram of 'ethic' is 'hetic' which is located in the answer.
'work' could be 'tally' (tally is a kind of work) and 'tally' is located in the remaining letters.
'father' could be 'pa' (pa can mean dad or father) and 'pa' is found within the answer.
'and' could be 'n' (common abbreviation for 'and') and 'n' is found within the answer.
The remaining letters 're' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for parenthetically that I've seen before include "(sic)" , "as an aside" , "A number here may appear this way!" .)