Ape noted in brown log-book, every so often (6)
I believe the answer is:
bonobo
'ape' is the definition.
(I know that bonobo is a type of common chimpanzee)
'brown log-book every so often' is the wordplay.
'every so often' indicates alternate letters.
'brown'+'log'+'book'='brownlogbook'
The alternate letters of 'brownlogbook' are 'BONOBO'.
'noted in' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for bonobo that I've seen before include "our nearest relative" , "Small chimpanzee" .)