I got IELTS General 6.5 overall but 5.5 in writing: is that enough for Canada PR?

Take listening 7.0, reading 6.5, speaking 6.5 and writing 5.5. That is CLB 7 listening, CLB 8 reading, CLB 8 speaking and CLB 6 writing. The Federal Skilled Worker Program needs CLB 7 in all four, so you are not eligible for it. The Canadian Experience Class needs CLB 7 for TEER 0 or 1 jobs and CLB 5 for TEER 2 or 3, and the Federal Skilled Trades Program needs CLB 5 speaking and listening with CLB 4 reading and writing (IRCC).

For a single applicant those four scores earn 72 CRS points for language. Raising writing to 6.0 (CLB 7) adds 8, to 80, and makes you FSW-eligible. CLB 7 or more in all four abilities also unlocks the skill-transferability points that combine language with education or foreign work experience: 13 or 25 points per combination below CLB 9, 25 or 50 at CLB 9 in all four.

Retake the full test: One Skill Retake does not count for Express Entry. Results must be less than two years old when you create your profile and when you apply for PR. PTE Core is the alternative; CLB 7 there is reading 60, writing 69, listening 60 and speaking 68 (IELTS General vs PTE Core for Canada).

Writing is the usual blocker at CLB 7 and CLB 9 (IELTS 7.0). Get two General Training letters and essays scored before you rebook: free IELTS mock test. Immigration rules change; confirm on IRCC before you apply. This is general information, not immigration advice.