Lee's hay ruined hair (7)
I believe the answer is:
eyelash
'hair' is the definition.
(I know that eyelash is a type of hair)
'lee's hay ruined' is the wordplay.
'ruined' indicates anagramming the letters.
'lees'+'hay'='leeshay'
'leeshay' is an anagram of 'EYELASH'.
(Other definitions for eyelash that I've seen before include "Row of facial hairs" , "maybe one drops with a wink" , "Say heel (anag)" , "batter" , "Short facial hair" .)