Fish left a piece of gymnastic equipment (7)
I believe the answer is:
barbell
'equipment' is the definition.
(barbell is a kind of equipment)
'fish left' is the wordplay.
'fish' becomes 'barbel' (I've seen this before).
'left' becomes 'l' (common abbreviation).
'barbel'+'l'='BARBELL'
'a piece of gymnastic' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for barbell that I've seen before include "One may be seen in a gym" , "equipment in gym" , "Weightlifting apparatus" , "One gets extremely loaded" , "Weight lifter's equipment" .)