Expected investigation in which lab is involved (8)
I believe the answer is:
probable
'expected' is the definition.
(thesaurus)
'investigation in which lab is involved' is the wordplay.
'investigation' becomes 'probe' (synonyms).
'in which' is an insertion indicator.
'is involved' is an anagram indicator (involved can mean confusing or complex).
'lab' is an anagram of 'abl'.
'probe' enclosing 'abl' is 'PROBABLE'.
(Other definitions for probable that I've seen before include "Like to happen" , "Likely to be the case" , "Seeming to have a good chance of happening" , "Person most likely" , "on the cards" .)