Yes. From what I understand the a.com dns is not managed by the same f5 DNS/GTM device, so if this is the case create static target, so create A record wideip for test.sefi with Cname record pool with static target a.com. Just in case I will recomend to also create another wide ip for CNAME record type for test.sefi with the same CNAME pool as the A record wideip for test.sefi as some applications may make a CNAME DNS request.
If the F5 will manage also a.com, then you will also need to create A record wideip for a.com and use it as pool member for the Wide IP for test.sefi (not the static target).
This has the best explanation, even has pictures for what you want (Go to section " BIG-IP DNS load balancing > Wide IPs and pools"). I also recomend reading the whole guide as it is not so long and it covers most of the options for F5 DNS/GTM.
https://support.f5.com/csp/article/K55502976