Salesperson with rug comes up to interfere (6)
I believe the answer is:
tamper
'interfere' is the definition.
(I know that tamper is a more specific form of interfere)
'salesperson with rug comes up' is the wordplay.
'salesperson' becomes 'rep' (sales rep).
'with' is a charade indicator (letters next to each other).
'rug' becomes 'mat' (both are floor coverings).
'comes up' says the letters should be written backwards (in a down clue, letters go up).
'rep'+'mat'='repmat'
'repmat' back-to-front is 'TAMPER'.
'to' is the link.
(Other definitions for tamper that I've seen before include "Machine for compacting earth; interfere (with)" , "Interfere harmfully" , "Meddle harmfully" , "Interfere (with a thing)" , "Meddle or interfere with" .)