The most common and most likely answer to this crossword clue is the 7 letter word SLENDER
I've seen this crossword clue in The Daily Telegraph
S
L
E
N
D
E
R
More clues leading to the result SLENDER
- Mailer accepting Pound is rather fine
- Spare rooms at last given to uncle
- South bank is narrow
- Small Building Society, say, is barely sufficient
- Thin girl's bottom shown in poster
- Slim profits ultimately got by loan provider
- Slight fall finally contained by exporter
- Society, one advancing money, very small
- Thin line into transmitter
- Modest southern bank, perhaps
Buddy explains!

The straight part
We know that "slim" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case slim = slender.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 SLENDER mean?
SLENDER adjective- Thin; slim.
- Meagre; deficient
- (Gaelic languages) Palatalized.