This is the "An Apostle, Saint, Prophet or Sage" by Italian, Venetian. The painting consists of five separate pieces of canvas, which were probably glued to a wooden support. You'll notice that the architectural elements, like the arch, were likely painted by a specialist and then joined to the piece with the figure.
The proportions of the figure suggest that this picture was intended to be placed very high up in a church or chapel, where small details wouldn't be seen. The unidentified figure looks down and clasps a round shaft, possibly part of a key or staff. He may be a prophet or ancestor of Christ from an Old Testament story.
The painting is unusual because the architectural elements were painted rather than carved or modelled. This suggests that it's from the Veneto region in Italy, where canvas decorations became popular in churches during the late 16th century. The brushwork has more in common with contemporaries of Palma Giovane than Pordenone.
An Apostle, Saint, Prophet or Sage hangs in The National Gallery on Trafalgar Square, London — free to enter. Point your phone at any artwork there and audioguide.london plays a free audio guide in six languages — no app download needed.