You and I take no time with new exhaust (6)
I believe the answer is:
weaken
'exhaust' is the definition.
(thesaurus)
'you and i take no time with new' is the wordplay.
'you and i' becomes 'we'.
'no' suggests deleting specific letters.
'time' becomes 't' (abbreviation).
'with' says to put letters next to each other.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'take' with 't' taken away is 'ake'.
'we'+'ake'+'n'='WEAKEN'
(Other definitions for weaken that I've seen before include "Reduce in strength" , "Become more feeble" , "Lose strength" , "Become less strong" , "Make less strong" .)