Such a word may be used as a slogan (5)
I believe the answer is:
catch
'slogan' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for catch that I've seen before include "fellow hooked for matrimony?" , "Dismiss (batsman); break (in voice)" , "Ensnare" , "problem in small print?" , "Arrest" .)