The most common and most likely answer to this crossword clue is the 5 letter word LIVEN
L
I
V
E
N
More clues leading to the result LIVEN
Buddy explains!

The straight part
We know that "Make cheerful" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case make cheerful = liven.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 LIVEN mean?
LIVEN verb- To cause to be more lively, or to become more lively.
- To be alive; to have life.
- To have permanent residence somewhere, to inhabit, to reside.
- To survive; to persevere; to continue.
- To cope.
- To pass life in a specified manner.
- To spend, as one's life; to pass; to maintain; to continue in, constantly or habitually.
- To act habitually in conformity with; to practice; to exemplify in one's way of life.
- To outlast danger; to float (said of a ship, boat, etc).
- (followed by "on" or "upon") To maintain or support one's existence; to provide for oneself; to feed; to subsist.
- To make the most of life; to experience a full, rich life.