Plague in spleen etc, I suspect (10)
I believe the answer is:
pestilence
'plague' is the definition.
('pestilence' can be a synonym of 'plague')
'spleen etc i suspect' is the wordplay.
'suspect' is an anagram indicator.
'spleen'+'etc'+'i'='spleenetci'
'spleenetci' anagrammed gives 'PESTILENCE'.
'in' is the link.
(Other definitions for pestilence that I've seen before include "Fatal epidemic disease" , "that'll plague you" , "Epidemic disease with a high death rate" , "it's an agent of evil" , "dire horseman?" .)