Show exasperation after missing a fine practice shot (7)
I believe the answer is:
sighter
'practice shot' is the definition.
(I've seen this before)
'show exasperation after missing a fine' is the wordplay.
'show exasperation' becomes 'sigh' (an exasperated person might sigh).
'after' says to put letters next to each other.
'missing a fine' becomes 'ter' (I can't justify this - if you can you should give a lot more credence to this answer).
'sigh'+'ter'='SIGHTER'
(Other definitions for sighter that I've seen before include "Practice shot in archery" , "test firing" .)