Glaswegian, possibly, most involved in survey (8)
I believe the answer is:
scotsman
'glaswegian possibly' is the definition.
(I know that Glaswegian is a type of Scotsman)
'most involved in survey' is the wordplay.
'involved' indicates anagramming the letters (involved can mean confusing or complex).
'in' is an insertion indicator.
'survey' becomes 'scan' (I've seen this before).
'most' is an anagram of 'otsm'.
'otsm' placed inside 'scan' is 'SCOTSMAN'.
(Other definitions for scotsman that I've seen before include "Native of Edinburgh" , "'Billy Connolly or Sean Connery, say (8)'" , "Northerner" , "He could be Jock or Angus" , "See 15" .)