foo.clj

(transform
   [ALL
    (collect-one :foo)
    (collect-one :bar)]
   (fn [foo bar _]
     (transform [REST ALL]
       #(map (partial + foo) %)
       bar))
   [{:foo 1 :bar [[10] [2 3] [20 30]]}
    {:foo 2 :bar [[10] [4 5] [40 50]]}
    {:foo 3 :bar [[10] [6 7] [60 70]]}])
 ;; => [[[10] [3 4] [21 31]] [[10] [6 7] [42 52]] [[10] [9 10] [63 73]]]

(mapv (fn [{:keys [foo bar]}]
        (into [(first bar)]
          (map #(mapv (partial + foo) %))
          (rest bar)))
  [{:foo 1 :bar [[10] [2 3] [20 30]]}
   {:foo 2 :bar [[10] [4 5] [40 50]]}
   {:foo 3 :bar [[10] [6 7] [60 70]]}])
;; => [[[10] [3 4] [21 31]] [[10] [6 7] [42 52]] [[10] [9 10] [63 73]]]