One helped by experienced person — ergo, pet, possibly? (7)
I believe the answer is:
protege
'one helped by experienced person' is the definition.
(a protege has a more experienced mentor)
'ergo pet possibly?' is the wordplay.
'possibly?' indicates an anagram (I've seen 'possibly' mean this).
'ergo'+'pet'='ergopet'
'ergopet' with letters rearranged gives 'PROTEGE'.
(Other definitions for protege that I've seen before include "One under another's patronage" , "Favoured pupil" , "Someone supported by an influential patron" , "One guided and supported by another" , "Person who is helped or sponsored by another" .)