The most common and most likely answer to this crossword clue is the 6 plus 4 plus 4 letter word LARGER THAN LIFE
I've seen this crossword clue in The Daily Telegraph
L
A
R
G
E
R
T
H
A
N
L
I
F
E
More clues leading to the result LARGER THAN LIFE
- Extravagant circulation claim by another old American magazine?
- Exaggerated fear confused with real thing by left
- Exaggerated fear with all-nighter ruined
- Very imposing -- that's how actors are on the cinema screen
- Fearing hell, art extraordinarily exaggerated
- How someone on Mount Rushmore looks over the top
- Exaggerated energy after falling rather awkwardly
- Flair the angler wildly exaggerated
- Republican trapped by flagrant lie he wildly exaggerated
Buddy explains!

The straight part
We know that "Very imposing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case very imposing = larger than life.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.