Undertake to crack an egg, sweetheart! (6)

(Source: London Evening Standard)

"crack an egg" ⇒ anagram of "an egg"

"sweetheart" ⇒ heart of "sweet" ⇒ middle letter or letters of "sweet" ⇒ "e"

Anagram of "anegg" + "e", meaning "undertake" or "undertake to"

"engage"