Share a line, being sensible (8)
I believe the answer is:
rational
'sensible' is the definition.
('rational' is associated in meaning with 'sensible')
'share a line' is the wordplay.
'share' becomes 'ration' (ration is a kind of share).
'line' becomes 'l'.
'ration'+'a'+'l'='RATIONAL'
'being' is the link.
(Other definitions for rational that I've seen before include "Endowed with reason" , "Based on logic or reasoning" , "Thinking logically" , "Logical, reasoned" , "In accordance with logic" .)