Urge to cut back share? That's an overstatement (12)
I believe the answer is:
exaggeration
'an overstatement' is the definition.
('exaggeration' can be a synonym of 'overstatement')
'urge to cut back share?' is the wordplay.
'urge' becomes 'egg' (I've seen this before).
'to cut' becomes 'axe' (I've seen this before).
'back' is a reversal indicator.
'share?' becomes 'ration' (ration is a kind of share).
'egg'+'axe'='eggaxe'
'eggaxe' in reverse letter order is 'exagge'.
'exagge'+'ration'='EXAGGERATION'
'that's' acts as a link.
(Other definitions for exaggeration that I've seen before include "lie" , "overstating the case" , "Hyperbole" , "Overstatement - overestimate" , "Something more noticeable" .)