It's showing lack of respect in a junior (13)
I believe the answer is:
insubordinate
'junior' is the definition.
Both the answer and definition are adjectives. Perhaps they are linked in a way I don't understand?
'it's showing lack of respect in a' is the wordplay.
I cannot quite understand how this works, but
'of' could be 'o' and 'o' is located in the answer.
'in' is present in the answer.
'a' is within the answer.
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for insubordinate that I've seen before include "Not submissive to authority" , "Rebellious" , "Mutinous" , "Recalcitrant" , "Cheeky" .)