Queen punches popular trader in Reading (9)
I believe the answer is:
inference
'reading' is the definition.
(both can mean an interpretation of something)
'queen punches popular trader' is the wordplay.
'queen' becomes 'er' (abbreviation for Elizabeth Regina).
'punches' means one lot of letters goes inside another (punch can mean to create a hole in).
'popular' becomes 'in'.
'trader' becomes 'fence' (trader of stolen goods).
'in'+'fence'='infence'
'er' inserted inside 'infence' is 'INFERENCE'.
'in' is the link.
(Other definitions for inference that I've seen before include "Deduction from evidence" , "Niece fern (anag.)" , "Conclusion reached on the basis of evidence and reasoning" , "Deduction, conclusion" .)