Nasty stink over a snake (3)
I believe the answer is:
boa
'snake' is the definition.
(boa constrictor, type of snake)
'nasty stink over a' is the wordplay.
'nasty stink' becomes 'bo' (body odour. I am not sure about the 'nasty' bit.).
'over' says to put letters next to each other (in a down clue, some letters go over others).
'bo'+'a'='BOA'
Can you help me to learn more?
(Other definitions for boa that I've seen before include "One with scaly body" , "that's dangerous for South Americans" , "Non-venomous snake" , "feathers around the neck?" , "Python" .)