Call to stop unit returning — disgusting! (6)
I believe the answer is:
enough
'call to stop' is the definition.
I can't judge whether this defines the answer.
'unit returning disgusting' is the wordplay.
'unit' becomes 'one' (synonyms).
'returning' shows that the letters should be reversed in order.
'disgusting' becomes 'ugh'.
'one' in reverse letter order is 'eno'.
'eno'+'ugh'='ENOUGH'
Can you help me to learn more?
(Other definitions for enough that I've seen before include "As much as necessary" , "To the required extent" , "As much as required" , "As much as desired" , "Satisfactory quantity" .)