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 there's a link between them I don't understand?
'seem proud to be responsible for the' is the wordplay.
I cannot really see how this works, but
'be' could be 'rut' (rutting is a kind of being) and 'rut' is located in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
A single letter 's' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
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" .)