What does the cryptic crossword clue "Lowest part of engine thermostat (10)" mean?

The definition is "Lowest". The wordplay uses a hidden word. Hidden in "lowest part of engiNE THERMOSTat" The answer is NETHERMOST.

Lowest part of engine thermostat (10)

Times Cryptic #28623 | 8 Down | 2023-06-07 flower