So unwell having lost kilo (3)
I believe the answer is:
sic
'so' is the definition.
('so' in Latin)
'unwell having lost kilo' is the wordplay.
'unwell' becomes 'sick' (similar in meaning).
'having lost' is a deletion indicator.
'kilo' becomes 'k' (phonetic alphabet: alpha, bravo, charlie etc.).
'sick' with 'k' removed is 'SIC'.
(Other definitions for sic that I've seen before include "Written exactly thus" , "Thus among musicians" , "the reading is correct" , "Quoted exactly as in the original; so" , "Like" .)