The most common and most likely answer to this crossword clue is the 6 letter word MARINE
I've seen this crossword clue in The Daily Telegraph
M
A
R
I
N
E
More clues leading to the result MARINE
- Soldier, one buried in site of battle
- Le Pen for instance found in sea
- Airmen at sea, or soldier at sea
- Sea or river flooding American state
- Remain at sea – as one would?
- Sea horse in fragments
- Soldier encountering resistance in state
- Start of research into state of the sea
- Jolly type from India diving into French river
- US state keeps Republican jolly
Buddy explains!

The straight part
We know that "jolly" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case jolly = marine.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 MARINE mean?
MARINE noun- A soldier, normally a member of a marine corps, trained to serve on board or from a ship
- Capitalised in the plural A marine corps.
- A painting representing some marine subject.
- Belonging to or characteristic of the sea; existing or found in the sea; formed or produced by the sea.
- Relating to or connected with the sea (in operation, scope, etc.), especially as pertains to shipping, a navy, or naval forces.
- Used or adapted for use at sea.
- Inhabiting the high seas; oceanic; pelagic. (distinguished from maritime or littoral)
- Belonging to or situated at the seaside; maritime.