Don't pass out - simply admit defeat! (4,2)
I believe the answer is:
give in
'admit defeat' is the definition.
(I've seen this before)
'don't pass out simply' is the wordplay.
I cannot really see how this works, but
'pass' could be 'give' (giving is a kind of passing) and 'give' is found within the answer.
The remaining letters 'in' 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 give in that I've seen before include "Cease fighting" , "Surrender, yield" , "Cease arguing/fighting" , "Surrender or hand over" , "Surrender, acknowledge defeat" .)