Thus tie up with sympathy (6)
I believe the answer is:
solace
'sympathy' is the definition.
(thesaurus)
'thus tie up' is the wordplay.
'thus' becomes 'so' (synonyms).
'tie up' becomes 'lace' (I've seen this in another clue).
'so'+'lace'='SOLACE'
'with' is the link.
(Other definitions for solace that I've seen before include "Comfort at a time of sadness" , "Comfort in time of disappointment or sorrow" , "Comfort and reassurance" , "Something that comforts distress" , "Comport" .)