The most common and most likely answer to this crossword clue is the 4 letter word FUEL
I've seen this crossword clue in The Guardian
F
U
E
L
Buddy explains!

The straight part
We know that "be encouraging" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case be encouraging = fuel.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 FUEL mean?
FUEL noun- Substance consumed to provide energy through combustion, or through chemical or nuclear reaction.
- Substance that provides nourishment for a living organism; food.
- Something that stimulates, encourages or maintains an action.
- To provide with fuel.
- To exacerbate, to cause to grow or become greater.