What does the cryptic crossword clue "Doctor then signs letter that deals with stress (7,8)" mean?

The wordplay uses an anagram. anagram of THENSIGNSLETTER ("then signs letter") [anagram: "deals"] = TENSILESTRENGTH The answer is TENSILESTRENGTH.

Doctor then signs letter that deals with stress (7,8)

Guardian Cryptic #29639 | 20 Across | 2025-03-11 flower