What does the cryptic crossword clue "Grenade thrown — go on the defensive (2,5)" mean?

The definition is "Grenade". The wordplay uses an anagram. anagram of GRENADE ("Grenade") [anagram: "thrown -"] = ENGARDE The answer is ENGARDE.

Grenade thrown — go on the defensive (2,5)

Guardian Cryptic #25156 | 20 Down | 2010-11-01 flower