Foul left one surrounded by team (7)
I believe the answer is:
squalid
'foul' is the definition.
(thesaurus)
'left one surrounded by team' is the wordplay.
'left one' becomes 'li' (left abbreviation plus 1).
'surrounded by' indicates putting letters inside.
'team' becomes 'squad' ('squad' can be a synonym of 'team').
'li' going into 'squad' is 'SQUALID'.
(Other definitions for squalid that I've seen before include "Wretched, filthy" , "Mean and dirty" , "Morally repulsive" , "Extremely dirty" , "Poverty-stricken - filthy" .)