The most common and most likely answer to this crossword clue is the 6 letter word REDDER
I've seen this crossword clue in The Sunday Telegraph
R
E
D
D
E
R
More clues leading to the result REDDER
- More revolutionary, even after revolution
- More embarrassed, one way or another
- More like rubies, either way
- Showing more embarrassment, looking up and down
- More sore on the rise or fall?
- Further to left? In either direction, it’s the same
- Closer to claret than rosé, however you look at it
- Lecturer with degree for a more colourful example of 16
- Communists standing back to back become more embarrassed
- More embarrassed, even when upset
Buddy explains!

The straight part
We know that "Further to left?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case further to left? = redder.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 REDDER mean?
REDDER adjective- Having red as its color.
- (of hair) Having an orange-brown or orange-blond colour; ginger.
- (of a card) Of the hearts or diamonds suits. Compare black
- (often capitalized) Supportive of, related to, or dominated by a political party or movement represented by the color red:
- Amerind; relating to Amerindians or First Nations
- Of the lower-frequency region of the (typically visible) part of the electromagnetic spectrum which is relevant in the specific observation.
- Having a color charge of red.