Stuck around organ (5)
I believe the answer is:
clung
'stuck' is the definition.
('cling' can be a synonym of 'stick')
'around organ' is the wordplay.
'around' becomes 'c' (abbreviation for 'circa').
'organ' becomes 'lung' (lung is a kind of organ).
'c'+'lung'='CLUNG'
(Other definitions for clung that I've seen before include "Held on tightly" , "Held on desperately" , "Was emotionally close" , "Held on tight" .)