Airline with no snake! (3)
I believe the answer is:
boa
'snake' is the definition.
(boa is a kind of snake)
'airline with no' is the wordplay.
'airline' becomes 'ba' (British Airways).
'with' is an insertion indicator.
'no' becomes 'o' (resembles 0 - 'no' can mean 'zero').
'ba' placed around 'o' is 'BOA'.
(Other definitions for boa that I've seen before include "Python" , "One with scaly body" , "that's dangerous for South Americans" , "strangler" , "Large reptile" .)