Green’s Dictionary of Slang

an act of sexual fondling.

1952		K. Williams Diaries 4 May 76: Returned to Salisbury 8.10 train arriving 10 o’c. T[ouch] U[p]. on train with soldier. V. gay.
1977		A. Brooke Last Toke 141: Bitch could sure stan’ a touchin’ up.
1983		J. Byrell (con. 1959) Up the Cross 111: ‘Hope you’re not giving the nurses touch-ups’.