siderealx wrote:
The two middle clips are freeze frames from the preceeding and leading clips which are both Burns effect. So I want a single transition/dissolve to simply spread accross all of them if that makes sense!
Ah! Ok, then Tom's advice is a solid one.
To be more precise, select the first two clips, and make a compound; select the last two clips, and make another compound. Then apply a transition between both compounds.
TIP: before making each compound, you may want to augment the duration of the still image; make the compound and then trim it back to the original duration. This way you will be creating "handles", which will be of great use when creating the transition.