Man in lab is dishevelled (5)
I believe the answer is:
basil
'man' is the definition.
(I've seen this before)
'lab is dishevelled' is the wordplay.
'dishevelled' is an anagram indicator.
'lab'+'is'='labis'
'labis' anagrammed gives 'BASIL'.
'in' acts as a link.
(Other definitions for basil that I've seen before include "Saint" , "Herb - boy's name" , "Herb (from Fawlty Towers?)" , "A herb; Cardinal --- Hume" , "Aromatic herb in pesto" .)