Fellow to lumber endlessly about and flounder (6)
I believe the answer is:
fumble
'flounder' is the definition.
(thesaurus)
'fellow to lumber endlessly about' is the wordplay.
'fellow' becomes 'f' (abbreviation - of a society etc.).
'to' means one lot of letters go next to another.
'endlessly' means to remove the last letter.
'about' indicates anagramming the letters.
'lumber' with its final letter taken away is 'lumbe'.
'lumbe' is an anagram of 'umble'.
'f'+'umble'='FUMBLE'
'and' acts as a link.
(Other definitions for fumble that I've seen before include "Handle awkwardly, grope about" , "Mishandle" , "Grope clumsily" , "Grope around" , "Handle something awkwardly" .)