In Soho line's seen showing devotion (8)
I believe the answer is:
holiness
'devotion' is the definition.
(thesaurus)
'in soho line's seen' is the wordplay.
'in' indicates a hidden word.
'HOLINESS' can be found hidden inside 'soho lines seen'.
'showing' acts as a link.
(Other definitions for holiness that I've seen before include "purity" , "Goodness!" , "State of sanctity" , "State of spiritual excellence" , "Piety" .)