Gibbon, eg this wild one grabbed by tailless ape (9)
I believe the answer is:
historian
'gibbon eg' is the definition.
(I know that Edward Gibbon has the occupation historian)
'this wild one grabbed by tailless ape' is the wordplay.
'wild' indicates anagramming the letters.
'one' becomes 'i' (Roman numeral).
'grabbed by' indicates putting letters inside (inserted letters are grabbed inside).
'tailless' means to remove the last letter (the tail of the word is removed).
'ape' becomes 'orang' (orang-utan).
'orang' with its final letter taken away is 'oran'.
'i' inserted within 'oran' is 'orian'.
'this' anagrammed gives 'hist'.
'hist'+'orian'='HISTORIAN'
(Other definitions for historian that I've seen before include "chronicler" , "student of the past" , "One sort of academic" , "Past master" , "So thin air suits recorder and analyst of past events" .)