The most common and most likely answer to this crossword clue is the 4 plus 5 letter word IRON HORSE
I've seen this crossword clue in The Times
I
R
O
N
H
O
R
S
E
More clues leading to the result IRON HORSE
- Eg Clydesdale press first to show revolutionary engine
- Old puffer in club husky in voice
- Press cavalry to provide engine once
- Engine horn is or should be blown with energy
- Press hack, for example, loco!
- Golf club socks emblazoned with LNER’s last steam-powered locomotive
- Old engine or senior machine’s heart renovated
- I run up the train
- Press hack’s name associated with Express?
- Train wild rhinoceros to skip around
Buddy explains!
The straight part
We know that "revolutionary engine" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case revolutionary engine = iron horse.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.