Sailors who hum? They stimulate you (8,5)
I believe the answer is:
smelling salts
'they stimulate you' is the definition.
(smelling salts can stimulate or refresh someone)
'sailors who hum?' is the wordplay.
I cannot really understand how this works, but
'sailors' could be 'salts' (salt is a kind of sailor) and 'salts' is located in the answer.
'hum?' could be 'smell' (I've seen this before) and 'smell' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for smelling salts that I've seen before include "Preparation used to arouse consciousness" , "could bring you round" , "Substance once used to bring you round" , "Sal volatile" , "Restorative to be sniffed" .)