Thus I was first to get dirty (6)
I believe the answer is:
soiled
'dirty' is the definition.
('soiled' can be a synonym of 'dirty')
'thus i was first' is the wordplay.
'thus' becomes 'so' ('so' can be a synonym of 'thus').
'was first' becomes 'led'.
'so'+'i'+'led'='SOILED'
'to get' is the link.
(Other definitions for soiled that I've seen before include "Dirty, grimy" , "Stained and dirty" , "Made dirty" , "Dirtied" .)