Below are possible answers for the crossword clue Lacking muscle.
4 letter answer(s) to lacking muscle
WEAK
(used of verbs) having standard (or regular) inflection
(used of vowels or syllables) pronounced with little or no stress; "a syllable that ends in a short vowel is a light syllable"; "a weak stress on the second syllable"
deficient in intelligence or mental power; "a weak mind"
deficient in magnitude; barely perceptible; lacking clarity or brightness or loudness etc; "a faint outline"; "the wan sun cast faint shadows"; "the faint light of a distant candle"; "weak colors"; "a faint hissing sound"; "a faint aroma"; "a weak pulse"
deficient or lacking in some skill; "he's weak in spelling"
lacking bodily or muscular strength or vitality; "a feeble old woman"; "her body looked sapless"
likely to fail under stress or pressure; "the weak link in the chain"
not having authority, political strength, or governing power; "a weak president"