During training, there's nothing to shoot (3)
I believe the answer is:
pot
'shoot' is the definition.
(I've seen this in other clues)
'during training there's nothing' is the wordplay.
'during' indicates putting letters inside.
'training' becomes 'pt' (Physical Training).
'there's nothing' becomes 'o' (I've seen this in other clues).
'pt' placed around 'o' is 'POT'.
'to' is the link.
(Other definitions for pot that I've seen before include "Saucepan" , "Container for 23" , "Preserve; drug" , "Kitchen utensil or slang cannabis" , "...Karenina(Tolstoy)" .)