The most common and most likely answer to this crossword clue is the 5 letter word BASER
I've seen this crossword clue in The Times
B
A
S
E
R
Buddy explains!

The straight part
We know that "Lower" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lower = baser.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 BASER mean?
BASER adjective- Low in height; short.
- Low in place or position.
- Of low value or degree.
- Of low social standing or rank; vulgar, common.
- Morally reprehensible, immoral; cowardly.
- Inferior; unworthy, of poor quality.
- Designating those metals which are not classed as precious or noble.
- Alloyed with inferior metal; debased.
- Of illegitimate birth; bastard.
- Not classical or correct.
- Not held by honourable service.
- Of sound, a voice or an instrument, low in pitch or frequency.