In temper, find fault with weight (7)
I believe the answer is:
tonnage
'weight' is the definition.
(I've seen this before)
'in temper find fault with' is the wordplay.
'in' indicates putting letters inside.
'temper' becomes 'tone' (both can mean temperament or attitude).
'find fault with' becomes 'nag' (I've seen this in another clue).
'tone' enclosing 'nag' is 'TONNAGE'.
(Other definitions for tonnage that I've seen before include "No agent (anag)" , "Weight of cargo - ship's carrying capacity" , "Measure of cargo space" , "Capacity of ship" , "Ship's size or carrying capacity" .)