In conclusion, effort's welcomed (6)
I believe the answer is:
trendy
'in' is the definition.
(thesaurus)
'conclusion effort's welcomed' is the wordplay.
'conclusion' becomes 'end' (end is a kind of conclusion).
'effort' becomes 'try' ('try' can be a synonym of 'effort'**).
'welcomed' indicates putting letters inside.
'end' inserted within 'try' is 'TRENDY'.
(Other definitions for trendy that I've seen before include "Up to date, fashionable" , "Stylish" , "In accordance with the latest fad" , "Informally, following the fashions" , "Hot" .)