This clue uses multiple techniques: homophone (sound-alike words), container (one part goes inside another), and deletion (removing outer letters). Look for words that indicate sounds, containment, and removal of edges.
'Caught' suggests a homophone - think of what 'you' sounds like as a letter, and note it appears 'twice'. 'Drawn in by' indicates one element contains another. 'Unframed' means remove the outer letters from a word. You need to find what 'group of students' refers to, then see how 'unframed Dali' fits with the rest.
Answer: UNUSUAL | U-U (the letter 'you' heard twice) containing NUS (National Union of Students), plus AL from 'Dali' with outer letters D and i removed ('unframed'). So: U(NUS)U + AL = UNUSUAL