In plain words
But one who controls the senses by the mind and, without attachment, engages the organs of action in karma-yoga is superior, Arjuna.
Word for word
But he who, having controlled the senses by the mind, O Arjuna, undertakes karma-yoga with the organs of action, unattached, he excels.
The commentators
Bhagavadgītābhāṣyam· bhāṣya
यस्तु पुनः कर्मण्यधिकृतः अज्ञः बुद्धीन्द्रियाणि मनसा नियम्य आरभते अर्जुन कर्मेन्द्रियैः वाक्पाण्यादिभिः । किमारभते इत्याह — कर्मयोगम् असक्तः सन् फलाभिसन्धिवर्जितः सः विशिष्यते इतरस्मात् मिथ्याचारात् ॥ ७ ॥
In plain words
But take the other man: he is fit for action and he does not yet know, so he holds the knowing senses in with the mind and then sets to work, Arjuna, with the organs of action — speech, hands, and the rest. Sets to work at what? At karma-yoga, unattached, with no eye on what the work will pay him. He is the better of the two — better than the one whose conduct is a lie.
Close to the Sanskrit
But he who, on the other hand, being qualified for action and not knowing, having restrained the knowing senses by the mind, begins, O Arjuna, with the organs of action — speech, hands and the rest. What does he begin? He says: karma-yoga, being unattached, that is, free from any aim at the fruit. He is distinguished from the other, from the man of false conduct.