What a pin-up might feel in the air? (3)
I believe the answer is:
nip
'what a pin-up might feel in the air?' is the definition.
I can't tell whether this definition defines the answer.
'what a pin-up' is the wordplay.
'what a pin' becomes 'pin'.
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'pin' reversed gives 'NIP'.
Can you help me to learn more?
(Other definitions for nip that I've seen before include "Pinch; bite" , "Swift bite" , "Small drink or small bite" , "severe cold" , "Catch" .)