The most common and most likely answer to this crossword clue is the 4 letter word TITO
I've seen this crossword clue in The Guardian
T
I
T
O
More clues leading to the result TITO
- WW2 leader’s some competitor!
- Revolutionary element to fight it out
- Old marshal and sea god RN separately dismissed
- Marshal competitors needing to strip off
- Communist leader of the highest quality stripped of all power
- Former leader of country, past it, obviously hides
- He opposed Stalin and survived to write about it
- Bird's love for Yugoslav leader
- Tax he removed with old statesman
- Yugoslav Marshal adapted to it
Buddy explains!

The straight part
We know that "Marshal" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case marshal = tito.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.