Tailored coat: try new shape (7)
I believe the answer is:
octagon
'shape' is the definition.
(octagon is a kind of polygon)
'tailored coat try new' is the wordplay.
'tailored' indicates anagramming the letters (the letters are customised ).
'try' becomes 'go' (both can mean an attempt).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'coat' is an anagram of 'octa'.
'octa'+'go'+'n'='OCTAGON'
(Other definitions for octagon that I've seen before include "Shape of a square with the corners cut off" , "plane figure" , "An eight-sided polygon" , "regular form" , "Geometric figure with eight sides" .)