Immobilise a player in distress, grasping top of shin (8)
I believe the answer is:
paralyse
'immobilise' is the definition.
(paralysing is a kind of immobilizing)
'a player in distress grasping top of shin' is the wordplay.
'in distress' indicates an anagram.
'grasping' is an insertion indicator.
'top of' says to take the initial letters.
The first letter of 'shin' is 's'.
'a'+'player'='aplayer'
'aplayer' is an anagram of 'paralye'.
'paralye' placed around 's' is 'PARALYSE'.
(Other definitions for paralyse that I've seen before include "Cause to be immobile" , "Cripple, incapacitate" , "Immobilise a person" , "Render immobile" , "make still" .)