Objection about one lake being made (5)
I believe the answer is:
built
'being made' is the definition.
(I've seen this before)
'objection about one lake' is the wordplay.
'objection' becomes 'but' (as in 'no ifs, no buts').
'about' indicates putting letters inside.
'one' becomes 'i' (Roman numeral).
'lake' becomes 'L' (geographical abbreviation).
'i'+'l'='il'
'but' placed around 'il' is 'BUILT'.
(Other definitions for built that I've seen before include "Made by combining materials and parts" , "assembled" , "put together" , "Erected" , "Raised" .)