Just find the right synonyms to the two words in the clue and then add them together to make one longer word. The longer word is the answer.
I will give you the number of letters and the first letters.
-1.Fourth + Last. 7,5,q,f
-2.Observed + Ashes. 3,4,s,d
-3.Rent + Grasp. 5,4,l,h
-4.Portion + Cliff. 4,5,p,r
-5.Finish + Rage. 3,5,e,a
-6.Terrain + Plummet. 4,4,l,f
7.Concise + Lawsuit. 5,4,b,c
8.Below + Envelop. 5,5,u,c
-9.Molar + Choose. 5,4,t,p
-10.Terrapin + Nape. 6,4,t,n