The most common and most likely answer to this crossword clue is the 4 letter word SCOW
I've seen this crossword clue in Financial Times
S
C
O
W
More clues leading to the result SCOW
- Flat-bottomed boat made by firm in the Devon area
- Almost lower boat
- Grimacing, being devoid of fish in boat
- Boat from south Jersey or Guernsey?
- Small beast is lighter
- Start to sink lower in boat
- Bosun’s heart is with lower flat- bottomed boat
- Lighter, small Jersey perhaps
- US yacht is daunting, stem to bow
- Sark boatless, Jersey or Guernsey getting boat
Buddy explains!

The straight part
We know that "Lighter" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lighter = scow.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does SCOW mean?
SCOW noun- A large flat-bottomed boat, having broad, square ends.
- To transport in a scow.