Here - suppression, means destruction of Radar, which disable SAM system and HARM don't cause shut down of Radar.
SAM operator shut down Radar to avoid ARM, once ARM become useless, they turn on Radar back, cause huge issues to USAF, and US developed a new tactics.
''In the 1990s, common wild weasel tactic was to use HARMs and cluster bombs together in a hunter-killer pair. The guy with the HARMs would fire at a SAM site(say a SA-2, SA-3, SA-6, etc.), and the guy with the cluster bombs would roll in and destroy the grouping after the SAM was forced into suppression.''
Here I think keyword is cluster bombs. When SAM operator shut down Radar, it provide a gap[sam inactive] and USAF send bomber to hell rain the entire area, with multiple effect, [google cluster bombs and why it banned] and rest job can be done by strike aircraft.
This tactics too old, and countries developed multiple layers of SAM or A2/AD systems. Even US developed new versions of harm, f35, f22, f18g etc.