Exercise set working for main group (7)
I believe the answer is:
peloton
'main group' is the definition.
I know nothing about this answer so I can't judge whether this works.
'exercise set working' is the wordplay.
'exercise' becomes 'pe' (Physical Education).
'set' becomes 'lot' (synonyms).
'working' becomes 'on' (e.g. a machine is working or on).
'pe'+'lot'+'on'='PELOTON'
'for' is the link.
Can you help me to learn more?
(Other definitions for peloton that I've seen before include "cyclists in bunch" , "Main group of cyclists in a race" , "Racing cyclists" , "Main packed group in a cycle race" , "Main body of riders in a cycle race" .)