General "mending":
* Pag-aayos (formal) - This is the most general term, meaning "repairing" or "fixing."
* Pagkukumpuni (formal) - This word is closer to "mending" and implies a more precise repair.
* Pagtatahi (formal) - This means "sewing" and is specifically used for mending clothes.
Specific contexts:
* Pag-aayos ng damit - "Mending clothes"
* Pag-aayos ng sirang bagay - "Fixing a broken thing"
* Pag-aayos ng relasyon - "Repairing a relationship"
The best translation will depend on the specific context of your sentence.