Indecent playing alone in tub embracing blokes (13)
I believe the answer is:
unmentionable
'indecent' is the definition.
(thesaurus)
'playing alone in tub embracing blokes' is the wordplay.
'playing' is an anagram indicator.
'embracing' means one lot of letters goes inside another.
'blokes' becomes 'men' (I've seen this in other clues).
'alone'+'in'+'tub'='aloneintub'
'aloneintub' with letters rearranged gives 'untionable'.
'untionable' placed around 'men' is 'UNMENTIONABLE'.
(Other definitions for unmentionable that I've seen before include "Forbidden as a topic of conversation" , "Not fit to be referred to" , "Taboo" .)