Cold and unproductive, but honest (5)
I believe the answer is:
clean
'honest' is the definition.
(I've seen this before)
'cold and unproductive' is the wordplay.
'cold' becomes 'C' (eg on taps).
'and' is a charade indicator (letters next to each other).
'unproductive' becomes 'lean' (I've seen this before).
'c'+'lean'='CLEAN'
'but' acts as a link.
(Other definitions for clean that I've seen before include "Free from dirt; well defined" , "not polluted" , "Squeakily hygienic?" , "Quite" , "not spotted" .)