Its not a radome for air to air radar, its a laser target designator for ground attack.
A designator, or a marked target seeker? Something akin to the Pave Penny pod used by the A-10? The opening seems a bit small for a designator, which would be akin to the Pave Tack (which was hugh!) used by the F-111 and F-4, or the LANTIRN targeting pod used on F-15E and F-16. (and F-14).