Abuse men installing a protective material (9)
I believe the answer is:
insulator
'protective material' is the definition.
(material which protects or insulates)
'abuse men installing a' is the wordplay.
'abuse' becomes 'insult' (synonyms).
'men' becomes 'OR' (Other Ranks: non-commissioned soldiers).
'installing' indicates putting letters inside (inserted letters are installed).
'insult'+'or'='insultor'
'insultor' going around 'a' is 'INSULATOR'.
(Other definitions for insulator that I've seen before include "Non-conducting material" , "safety device" , "Non-conducting solid" , "Non-conductor" .)