The most common and most likely answer to this crossword clue is the 5 plus 4 letter word OLIVE DRAB
I've seen this crossword clue in Independent
O
L
I
V
E
D
R
A
B
More clues leading to the result OLIVE DRAB
- Uniform material was adopted by soldiers and sailor
- Dull colour of old poet, ill, withdrawn
- Female poet turning up in a dull green colour
- Old poet wrong about uniform colour
- Grey-green wild boar gobbles Old Nick up
- Green colour of a lovebird flying around
- Ban demon duck rising in shade
- A lovebird in a frenzy can make an American colour
- Colour as it happens found in unconventional board
- Local monster of rampant shade of green
Buddy explains!

The straight part
We know that "uniform colour" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case uniform colour = olive drab.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.