The most common and most likely answer to this crossword clue is the 6 letter word TOSSED
I've seen this crossword clue in The Sunday Telegraph
T
O
S
S
E
D
Buddy explains!
The straight part
We know that "Cast was uneasy when resting" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cast was uneasy when resting = tossed.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 TOSSED mean?
TOSSED verb- To throw with an initial upward direction.
- To lift with a sudden or violent motion.
- To agitate; to make restless.
- To subject to trials; to harass.
- To flip a coin, to decide a point of contention.
- To discard: to toss out
- To stir or mix (a salad).
- (British slang) To masturbate
- To search (a room or a cell), sometimes leaving visible disorder, as for valuables or evidence of a crime.
- To roll and tumble; to be in violent commotion.
- To be tossed, as a fleet on the ocean, or as a ship in heavy seas.
- To keep in play; to tumble over.
- To peak (the oars), to lift them from the rowlocks and hold them perpendicularly, the handle resting on the bottom of the boat.
- (British slang) To drink in large draughts; to gulp.