1) Abstract 2) Act the petty thief 3) Cabbage 4) Commit petty theft 5) Emulate raffles 6) Filch 7) French word used in English 8) Hook 9) Indulge in petty theft 10) Lift 11) Lift, so to speak 12) Nobble 13) Pinch 14) Purloin 15) Shoplift 16) Snarf 17) Sneak 18) Steal 19) Steal bit by bit 20) Steal pettily Found on https://www.crosswordclues.com/clue/pilfer
• (v. t.) To take by petty theft; to filch; to steal little by little. • (v. i.) To steal in small quantities, or articles of small value; to practice petty theft. Found on http://thinkexist.com/dictionary/meaning/pilfer/
Pil'fer intransitive verb [ imperfect & past participle Pilfered ; present participle & verbal noun Pilfering .] [ Old French pelfrer . See Pelf .] To steal in small quantities, or articles of small value; to practice petty ... Found on http://www.encyclo.co.uk/webster/P/88
Pil'fer transitive verb To take by petty theft; to filch; to steal little by little. « And not a year but pilfers as he goes Some youthful grace that age would gladly keep.» Cowper. Found on http://www.encyclo.co.uk/webster/P/88