Disable mast originally handling mobile phone (9)
I believe the answer is:
hamstring
'disable' is the definition.
(thesaurus)
'mast originally handling mobile phone' is the wordplay.
'originally' says to take the initial letters.
'mobile' indicates an anagram.
'phone' becomes 'ring' ('ring' can be a synonym of 'phone'**).
The initial letter of 'handling' is 'h'.
'mast'+'h'='masth'
'masth' is an anagram of 'hamst'.
'hamst'+'ring'='HAMSTRING'
(Other definitions for hamstring that I've seen before include "hamper" , "Tendons at back of the knee" , "Tendon at back of knee" , "Impede" , "Tendon behind the knee" .)