FRT is the time taken by the agent to respond to a ticket, the first time. The standard FCT is 15 minutes. It’s important to keep it as low possible as customers get frustrated when the first response from support takes a long time.
An agent’s FCT should be within the response due time (configured in the SLA policy). If an agent has a high average FCT but her tickets violate SLAs often, then it’s a sign that she has more tickets than she can handle.