Amorous activity at Oxford that all can sport? (6)
I believe the answer is:
unisex
'that all can sport?' is the definition.
(that which can be worn or sported by men or women)
'amorous activity at oxford' is the wordplay.
I cannot really understand how this works, but
'activity' could be 'sex' (sex activity is a kind of activity) and 'sex' is found in the answer.
The remaining letters 'uni' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
(Other definitions for unisex that I've seen before include "For both males and females" , "Suitable for male and female" , "like St Hilda's now, > but not St Trinian's!" , "good for both partners" , "for boys and girls" .)