Get on with backward member (3)
I believe the answer is:
gel
'get on' is the definition.
The definition and answer can be both related to bodily activities as well as being verbs in their base form.
Perhaps there's a link between them I don't understand?
'backward member' is the wordplay.
'backward' is a reversal indicator.
'member' becomes 'leg' (leg is a kind of member).
'leg' in reverse letter order is 'GEL'.
'with' is the link.
Can you help me to learn more?
(Other definitions for gel that I've seen before include "Take form" , "Leg (anag.)" , "Leg it back to get some for your hair" , "well-spoken deb?" , "Viscid substance" .)