अन्वयः

श्यामा beautiful, वरवर्णिनी a lady of lovely complexion, जानकी Janaki, सन्ध्याकालमनाः at the time of twilight, शुभजलाम् sacred waters, इमां नदीम् this river, सन्ध्यार्थे for performing evening ritual, ध्रुवम् surely, एष्यति come.

M N Dutt

(The morning has set in) and surely the beautiful and graceful daughter of Janaka fond of performing morning ablutions, shall come to this river of pure water to perform them. "Sandhyā literally means the point of time which connect day and night. It however, generally means the period after sunset and before the night sets. But here with reference to the speech which Hanumān began by the end of night, it means the morning.

Summary

Surely that lady of lovely complexion, the beautiful Janaki will come to this river flowing with sacred waters for performing the evening rituals.

पदच्छेदः

संध्याकालमनाः	संध्या–काल–मनस् (१.१)
श्यामा	श्याम (१.१)
ध्रुवम्	ध्रुवम् (अव्ययः)
एष्यति	एष्यति (√इ लृट् प्र.पु. एक.)
जानकी	जानकी (१.१)
नदीं	नदी (२.१)
चेमां	च (अव्ययः)–इदम् (२.१)
शिवजलां	शिव–जल (२.१)
संध्यार्थे	संध्या–अर्थ (७.१)
वरवर्णिनी	वरवर्णिनी (१.१)

छन्दः

अनुष्टुप् [८]

छन्दोविश्लेषणम्

१	२	३	४	५	६	७	८
सं	ध्या	का	ल	म	नाः	श्या	मा
ध्रु	व	मे	ष्य	ति	जा	न	की
न	दीं	चे	मां	शि	व	ज	लां
सं	ध्या	र्थे	व	र	व	र्णि	नी