Heard member of upper house is unproductive (6)
I believe the answer is:
barren
'unproductive' is the definition.
(synonyms)
'heard member of upper house' is the wordplay.
'heard' indicates a 'sounds like' (homophone) clue.
'member of upper house' becomes 'baron' (member of the House of Lords).
'baron' sounds like 'BARREN'.
'is' acts as a link.
(Other definitions for barren that I've seen before include "Unproductive of life" , "Unable to bear young" , "Unable to reproduce, infertile" , "Not producing fruit" , "Bleak, lifeless" .)