What does the cryptic crossword clue "Show Dirty Harry is half-hearted (4,5)" mean?

The wordplay uses a charade (building blocks). BLUE (synonym="dirty") + PE (synonym="PE") + TER (synonym="TER") = BLUEPETER The answer is BLUEPETER.

Show Dirty Harry is half-hearted (4,5)

Guardian Cryptic #29194 | 16 Down | 2023-10-06 flower