Bottom, giving no thought to one’s performance? (4-2-3-5)
I believe the answer is:
seat-of-the-pants
'performance?' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'bottom giving no thought to one's' is the wordplay.
I cannot quite see how this works, but
'bottom' could be 'sea' (sea bottom is a kind of bottom) and 'sea' is found within the answer.
'no' could be 'o' (O resembles 0) and 'o' is present in the answer.
'one' could be 'the' (both can introduce a definite example of something) and 'the' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for seat-of-the-pants that I've seen is " Instinctive".)