Crockery containing one form of exercise (7)
I believe the answer is:
pilates
'exercise' is the definition.
(pilates is a type of exercise)
'crockery containing one form of' is the wordplay.
'crockery' becomes 'plate' (plate is a kind of crockery).
'containing' is an insertion indicator.
'one' becomes 'I' (Roman numeral).
'form of' becomes 's' (I can't justify this - if you can you should give a lot more credence to this answer).
'plate' going around 'i' is 'pilate'.
'pilate'+'s'='PILATES'
Can you help me to learn more?
(Other definitions for pilates that I've seen before include "Exercise system" , "regime for improved fitness" , "Ali's pet (anag) - exercise regime" , "attributed to Biblical procurator?" , "Holistic system of physical exercises" .)