Chap's working out trips for guardians of apples (10)
I believe the answer is:
hesperides
'guardians of apples' is the definition.
(group of nymphs in Greek myth)
'chap's working out trips' is the wordplay.
'chap's' becomes 'hes'.
'working out' becomes 'pe' (physical education).
'trips' becomes 'rides' (I've seen this before).
'hes'+'pe'+'rides'='HESPERIDES'
'for' acts as a link.
(Other definitions for hesperides that I've seen before include "Watchful nymphs" , "Sisters of Greek myth guarding golden apples" , "The golden apples of the - were taken by Heracles" .)