Stick getting a bit of tension out of muscle (4)
I believe the answer is:
glue
'stick' is the definition.
(to stick with glue)
'tension out of muscle' is the wordplay.
'tension' becomes 't' (abbreviation for surface tension).
'out of' indicates named letters should be taken away ('out of' can mean no longer having).
'muscle' becomes 'glute' (short for gluteus).
'glute' with 't' removed is 'GLUE'.
'getting a bit of' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for glue that I've seen before include "Gum" , "Sticky substance" , "agent with sticking power" , "Paste" , "Adhesive stuff" .)