Possible Clues:

• Morphing sci-fi creature
• The spearfish (anag) — mythical being that can change its form
• Fresh phase, it's adaptable, being capable of change
• Fictional figure able to change form at will — preheats fish (anag)
• Werewolf, e.g. ... or the one responsible for 20-, 34- and 41-Across?
• ... the fitness magazine hired a ___ to rebuild its brand