Force slippery character to show sense (4)
I believe the answer is:
feel
'sense' is the definition.
(I know that sense can be written as feel)
'force slippery character' is the wordplay.
'force' becomes 'F' (symbol used in Physics e.g. f=ma).
'slippery character' becomes 'eel' (slippery fish).
'f'+'eel'='FEEL'
'to show' is the link.
(Other definitions for feel that I've seen before include "Perceive by touch" , "16A [JUDGE]" , "Have sensation of" , "Instinct" , "Consider" .)