To stain badly in one place (7)
I believe the answer is:
station
'one place' is the definition.
(synonyms)
'to stain badly' is the wordplay.
'badly' indicates anagramming the letters.
'to'+'stain'='tostain'
'tostain' is an anagram of 'STATION'.
'in' acts as a link.
(Other definitions for station that I've seen before include "Train stop" , "Waterloo perhaps" , "Such as Victoria" , "Put" , "Base, post" .)