As far as new unit by lake (5)
I believe the answer is:
until
'as far as' is the definition.
(I've seen this before)
'new unit by lake' is the wordplay.
'new' indicates an anagram.
'by' is a charade indicator (letters next to each other).
'lake' becomes 'L' (geographical abbreviation).
'unit' anagrammed gives 'unti'.
'unti'+'l'='UNTIL'
(Other definitions for until that I've seen before include "Up to (a point in time)" , "Not beyond (hour)" , "Pending such time as" , "Before a given time" , "As far as" .)