On holiday, fiction is read primarily by detached person (7)
I believe the answer is:
outlier
'detached person' is the definition.
'outlier' can be an answer for 'person' (outlier is a kind of person). I'm not sure about the 'detached' bit.
'on holiday fiction is read primarily' is the wordplay.
'on holiday' becomes 'out' (I am not sure about this - if you are sure you should believe this answer much more).
'fiction' becomes 'lie' (I've seen this in other clues).
'primarily' says to take the initial letters.
The initial letter of 'read' is 'r'.
'out'+'lie'+'r'='OUTLIER'
'by' acts as a link.
Can you help me to learn more?
(Other definitions for outlier that I've seen before include "Rock formation" , "isolated example" , "Statistical anomaly" , "Remote member of a group" , "Exception" .)