The 28-year-old forward joined Exeter City on a free transfer in July 2021 and last season he helped the Grecians earn promotion to League One.
Brown has been in impressive form this season and has scored 14 goals in 32 outings for Exeter while laying on nine assists.
Portsmouth boss John Mousinho is keen to strengthen his attacking department before the end of the window.
And Brown’s performance in the league has not gone unnoticed, as Pompey are interested in signing the 28-year-old in the ongoing window.
Portsmouth have already signed Di’Shon Bernard on loan from Manchester United on deadline day and are pushing to sign the forward.
Both parties are negotiating the player’s transfer fee, but it has been claimed that they have yet to reach an agreement for the forward.
As the transfer window approaches its end, it is unclear whether Pompey will be able to complete the deal for Brown on time.
