The most common and most likely answer to this crossword clue is the 5 letter word TONED
I've seen this crossword clue in Independent
T
O
N
E
D
More clues leading to the result TONED
- Words on gift tag for Edmund went well
- Muscular flanks to expand under weight
- Buff spot on Edwardian screens
- Looking fit, if half unbuttoned
- Superbly muscled, but somewhat put on edge
- Pitch on first day in good condition
- One starts diet after end of workout to get this way
- Noted changes getting firm through exercise
- Firm‘s great deal with worker in rag trade?
- Addressing Kelly with firmness
Buddy explains!

The straight part
We know that "Muscular" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case muscular = toned.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 TONED mean?
TONED verb- To give a particular tone to
- To change the colour of
- To make (something) firmer
- To harmonize, especially in colour
- To utter with an affected tone.
- Having a (specified kind of) tone.
- Having defined or firm muscles; fit