Panties off, which is wise (7)
I believe the answer is:
sapient
'is wise' is the definition.
(similar in meaning)
'panties off' is the wordplay.
'off' indicates anagramming the letters.
'panties' anagrammed gives 'SAPIENT'.
'which' is the link.
(Other definitions for sapient that I've seen before include "Discerning" , "of great wisdom" , "Panties (anag)" , "Canny" , "Snipe at, being wise" .)