The most common and most likely answer to this crossword clue is the 12 letter word KINAESTHESIA
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Buddy explains!
The straight part
We know that "Sensing muscular effort" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sensing muscular effort = kinaesthesia.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 KINAESTHESIA mean?
KINAESTHESIA noun- Sensation or perception of motion.
- Proprioception or static position sense; the perception of the position and posture of the body; also, more broadly, including the motion of the body as well. See usage notes below.