A linseed rub may be unpleasant (11)
I believe the answer is:
undesirable
'unpleasant' is the definition.
(thesaurus)
'a linseed rub may be' is the wordplay.
'may be' indicates anagramming the letters.
'a'+'linseed'+'rub'='alinseedrub'
'alinseedrub' with letters rearranged gives 'UNDESIRABLE'.
(Other definitions for undesirable that I've seen before include "Not welcome" , "bad news" , "Not to be wished for" , "Not wanted" , "Objectionable person" .)