What does the cryptic crossword clue "What on earth's the attraction for entering exam? (1-5)" mean?

The wordplay uses a container (one word inside another). FOR (synonym="FOR") in GCE (synonym="GCE") = GFORCE The answer is GFORCE.

What on earth's the attraction for entering exam? (1-5)

Guardian Cryptic #26228 | 7 Down | 2014-04-08 flower