Group of biologists enter void without top-class guide (4,5)
I believe the answer is:
vade mecum
'guide' is the definition.
(thesaurus)
'group of biologists enter void without top-class' is the wordplay.
'group of biologists' becomes 'deme' (biological term for a group of related organisms).
'enter' is an insertion indicator.
'void' becomes 'vacuum'.
'without' is a deletion indicator.
'top-class' becomes 'u' (as in U and non-U speech).
'vacuum' with 'u' removed is 'vacum'.
'deme' inserted into 'vacum' is 'VADE-MECUM'.
(Other definitions for vade mecum that I've seen before include "guidebook" , "Handbook, guide" .)