The most common and most likely answer to this crossword clue is the 5 letter word REEDY
I've seen this crossword clue in The Daily Telegraph
R
E
E
D
Y
More clues leading to the result REEDY
- Too keen to eat something not good, like grass
- Like Bunter losing head, becoming weak and thin?
- Tall and thin? Wanting lots of food's not good
- Gourmand leaving starter to get thin
- Eyes bigger than stomach, missing starter to get thin
- Mike abandons correct piping
- Piping like a pig with no head?
- Like some of the wind cure Mike ignored
- Very eager to lose gram to get thin
- Thin and weak, wanting lots of food but no starter
Buddy explains!

The straight part
We know that "Thin and weak" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case thin and weak = reedy.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 REEDY mean?
REEDY adjective- Full of, or edged with, reeds.
- (of a sound or voice) High and thin in tone.
- (of a person) Tall and thin.
- Imperfectly welded together in masses of rods.