Difficult to swallow odd bits of Viagra in this university (7)
I believe the answer is:
harvard
'this university' is the definition.
(Harvard is an example)
'difficult to swallow odd bits of viagra' is the wordplay.
'difficult' becomes 'hard' ('hard' can be a synonym of 'difficult').
'to swallow' means one lot of letters goes inside another.
'odd bits of' means one should take alternating letters.
The alternating letters of 'viagra' are 'var'.
'hard' placed around 'var' is 'HARVARD'.
'in' is the link.
(Other definitions for harvard that I've seen before include "place of learning" , "Oldest US university" , "US Ivy League university" , "American university" , "Ivy league university in Cambridge, Massachusetts" .)