"explanation is lacking" is correct and usable in written English.
You can use it when there is an absence of explanation or understanding. For example, "The student submitted his essay but an explanation is lacking as to why he did not finish it on time."
A comprehensive explanation is lacking for the broad array of cognitive effects modulated by transcranial direct current stimulation (tDCS).
Carotid body denervation has been shown to have a profound effect on airway hyper-responsiveness in animal models but a mechanistic explanation is lacking.
This is in strong conflict with simulations of the formation of dark matter halos from cosmological simulations, indicating that an explanation is lacking for the formation of the suggested dark matter ring in Cl0024+17.
Groups of symptoms described in this pattern have appeared under different labels like "food intolerance," [18] "chronic pain syndrome" [19] or "medically unexplained symptoms," [20] meaning that a definite medical diagnosis explaining the symptoms is often not established and a reasonable organic explanation is lacking [21].
An explanation is lacking for this observation.
Due to these inconsistent results, a clear explanation is lacking.
Growth-inhibitory effects of the novel selective AAG8 antagonists in a breast cancer cell line has been documented, however, molecular explanation was lacking 14.
Although genetic explanations is lacking, there are considerable regional and ethnic variations in typical frequencies of many genotypes e.g., frequency of ACE II is higher in some regions of Oceania than most of Europe while athletes of north and east African descent excel in endurance events and those of west African descent excel in sprint events [67].
"But explanations are lacking at the White House". Well, those explanations are still lacking.
So far, the team has uncovered no predictor for who is most likely to remember something from their death, and explanations are lacking for why some people experience terrifying scenarios while others report euphoric ones.
Similar adaptive explanations are lacking for the remaining species, however.
