Celebrity by railway looked idealistic (6-4)
I believe the answer is:
starry-eyed
'idealistic' is the definition.
(thesaurus)
'celebrity by railway looked' is the wordplay.
'celebrity' becomes 'star' (I've seen this before).
'by' is a charade indicator (letters next to each other).
'railway' becomes 'ry' (abbreviation for railway).
'looked' becomes 'eyed' (eyeing is a kind of looking).
'star'+'ry'+'eyed'='STARRY-EYED'
(Other definitions for starry-eyed that I've seen before include "Naively enthusiastic" , "Full of unsophisticated optimism" , "Romantically optimistic" , "Naively idealistic" , "Out of touch with reality" .)