You get fed up with it changing to "stop" (5)
I believe the answer is:
tired
'you get fed up with it changing to stop' is the definition.
I can't judge whether this definition defines the answer.
'you get fed up with' is the wordplay.
'you' becomes 't' (I can't justify this - if you can you should give a lot more credence to this answer).
'get' says to put letters next to each other.
'fed up with' becomes 'ired' (I've seen this in another clue).
't'+'ired'='TIRED'
Can you help me to learn more?
(Other definitions for tired that I've seen before include "ready for bed" , "Worn out" , "Physically or mental weary" , "knackered" , "Played out" .)