Sight or smell (5)
I believe the answer is:
sense
I believe this is a double definition.
'sight' is the first definition.
(I know that sense is a type of detect)
'smell' is the second definition.
(I know that smell can be written as sense)
(Other definitions for sense that I've seen before include "may be common" , "eg Vision, hearing" , "Understand" , "Meaning - feeling" , "definition" .)