Drink inferior to sea water reportedly limited (4,4)
I believe the answer is:
tied down
'limited' is the definition.
(limit can mean to tie down or restrict)
'drink inferior to sea water reportedly' is the wordplay.
'drink' becomes 'down' (to down something can mean to drink it quickly).
'inferior to' says to put letters next to each other (in a down clue, some letters go below others).
'sea water' becomes 'tide'.
'reportedly' indicates a 'sounds like' (homophone) clue.
'tide' sounds like 'tied'.
'down' put after 'tied' is 'TIED DOWN'.
(Another definition for tied down that I've seen is " Committed to a decision".)