Pay attention and join the army in the wrong order (6)
I believe the answer is:
listen
'pay attention' is the definition.
(to listen to someone)
'and join the army in the wrong order' is the wordplay.
I cannot quite see how this works, but
'and' could be 'n' (common abbreviation for 'and') and 'n' is present in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
The remaining letters 'lise' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for listen that I've seen before include "Lend an ear (6)" , "Harken" , "what buggers do" , "Take notice" , "Give one's attention" .)