After hard work, a new catchphrase (6)
I believe the answer is:
slogan
'catchphrase' is the definition.
(eg a political catchphrase)
'after hard work a new' is the wordplay.
'after' means one lot of letters go next to another.
'hard work' becomes 'slog' (a slog is a long or difficult task).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'slog' put next to 'a' is 'sloga'.
'sloga'+'n'='SLOGAN'
(Other definitions for slogan that I've seen before include "Tag line" , "'Motto, watchword (6)'" , "Battle cry - advertising phrase" , "War cry - advertising jingle" , "Memorable advertising phrase" .)