Clue: The last ictodosaur, somewhat resilient (7)
Answer: ELASTIC
Explanation: Definition: re
A hidden answer ('somewhat') in 'th**E LAST IC**todosaur'. Why did Everyman choose the obscure ictodosaur rather than, say, the better known icthyosaur (or, to take a quite different tack, ice-age)? Wikipedia does not even mention the word, and a search turns up mainly dictionary definitions (perhaps it is a discredited interpretation of the fossil record?)