Sensible share taken by Capone (8)
I believe the answer is:
rational
'sensible' is the definition.
(associated in meaning)
'share taken by capone' is the wordplay.
'share' becomes 'ration' (a ration is a share of a limited resource).
'taken by' means one lot of letters go next to another.
'capone' becomes 'Al' (gangster Al Capone).
'ration'+'al'='RATIONAL'
(Other definitions for rational that I've seen before include "Clear-headed" , "Thinking logically" , "Reasonable, logical" , "Based on logic or reasoning" , "Endowed with reason" .)