Seem proud to be responsible for the hold-up (5)
I believe the answer is:
strut
'hold-up' is the definition.
Both the answer and definition are singular nouns.
Maybe they are linked in a way I don't understand?
'seem proud to be responsible for the' is the wordplay.
I cannot quite see how this works, but
'be' could be 'rut' (rutting is a kind of being) and 'rut' is found within the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found in the answer.
A single letter 's' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for strut that I've seen before include "Supportive member" , "Walk pompously" , "Swagger; bracing bar" , "Stalk" , "Walk with proud and conceited gait" .)