Length - approximate and free (9)
I believe the answer is:
footloose
'free' is the definition.
(I've seen this before)
'length approximate and' is the wordplay.
I cannot quite understand how this works, but
'length' could be 'l' (abbreviation in geometry) and 'l' is present in the answer.
'and' could be 'too' and 'too' is located in the remaining letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for footloose that I've seen before include "Free from ties" , "Able to travel freely and do as one pleases" , "without responsibility?" , "Fancy-free" , "Eager to travel" .)