First of shirts with dirt, say, held up has blurred mark (6)
I believe the answer is:
smudge
'blurred mark' is the definition.
(I've seen this before)
'first of shirts with dirt say held up' is the wordplay.
'first of shirts' becomes 's' (1st letter of 'shirts').
'with' means one lot of letters go next to another.
'dirt' becomes 'mud' (mud is a kind of dirt).
'say' becomes 'eg' (both can mean for example).
'held up' says the letters should be written backwards.
'eg' in reverse letter order is 'ge'.
's'+'mud'+'ge'='SMUDGE'
'has' is the link.
(Other definitions for smudge that I've seen before include "Messy smear caused by rubbing" , "Blur, blot" , "Messy mark" , "Blotch" , "Smeared blot" .)