### Clue: Extremely fastidious about Irish volunteers needing ID to provide medical assistance (5,3)
### Answer: FIRST AID 
 ### Explanation: Definition: medical assistance
 F,S[the outermost letters of,(Extremely) "fastidious"] **containing**(about) IR(abbrev. for "Irish") + TA(abbrev. for the Territorial Army consisting of volunteers) + ID.