Of a root which has ṇa in its original enunciation, when it comes after a cause of such change standing in an upasarga , even though the word be not a samāsa , the na is changed to ṇa,
The word णोपदेश means a root which is enunciated in the Dhatupatha with an initial ण ॥ Thus प्रणमति 'he bows'. परिणमति, प्रणायकः 'a leader' परिणायकः &c.
Why do we say \after an Upasarga\? Observe प्रनायकः = प्रगता नायका अस्माद् देशात् 'a country without a leader'. Here the word प्र is not an upasarga, but a mere nipata. See 1.4.57, 1.4.58 and 1.4.59. In fact, प्र is upasarga here with regard to गत understood, and not with regard to नी ॥
Why do we say \even when it is not a compound?\ Because by context, the anuvritti of the word पूर्वपद, which is current throughout this subdivision, would have been understood in this sutra also, and the rule would have applied to samasas only, for there only we have purvapada. By using the word असमासे it is shown that the adhikara of purvapada ceases, and the rule applies to non-compounds also where there is no पूर्वपद ॥
Why do we say \having ण in Upadesa\? Observe प्रनर्दति, प्रनर्दितुम्, प्रनर्दकः ॥ For the root नर्द is recited in Dhatupatha with न ॥ There are eight such roots नर्द्, नाट्, नाथ्, नाध्, नन्द्, नक्क्, नॄ, नृत् ॥ See 6.1.65.,