This is one of the most reassuring promises in the entire Gita. Krishna says: those who think of me with undivided attention — I personally take care of everything they need. What they lack, I bring to them. What they have, I protect.
The word 'yoga-kshemam' is specific. 'Yoga' means gaining what you do not yet have. 'Kshema' means safeguarding what you already have. Krishna says he handles both. Like a mother who feeds her infant, watches over it while it sleeps, and shields it from every harm — without being asked.
The condition is 'ananyah' — undivided. Not split between ten different sources of security. When the mind settles on one direction, the way a lamp flame stands still in a windless room, that focused devotion activates this promise.