Honest heterosexual a miserable item, oddly (8,2,1,3)
I believe the answer is:
straight as a die
'honest' is the definition.
(I've seen this before)
'heterosexual a miserable item oddly' is the wordplay.
'heterosexual' becomes 'straight' (similar in meaning).
'miserable' becomes 'sad' (similar in meaning).
'oddly' indicates alternate letters (letters in the odd-numbered positions are used).
The alternating letters of 'item' are 'ie'.
'straight'+'a'+'sad'+'ie'='STRAIGHT AS A DIE'
(Other definitions for straight as a die that I've seen before include "not crooked" , "honest" .)