Everton are set for a further payment on Gareth Barry if the midfielder re-signs for West Brom.
The 38-year-old left Goodison Park to join the Baggies back in July 2017 for an undisclosed fee as the veteran was seeking more regular first team football, despite Ronald Koeman being keen to keep hold of the former Man City and Aston Villa man.
Barry was released by Albion in June of this year, but is now being linked with a return to the club with the offer of a new contract reportedly in the offing.
However, a clause in the midfielder's previous deal with Everton means the Blues would be due a further payment from the midlands club if they were to re-sign the experienced former England international.
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Slaven Bilic revealed to BBC WM that the clause is currently holding the deal back, although the West Brom board are doing everything they can to rectify the situation - with the two clubs already in touch over the midfielder.
"It's frustrating for us and for him," the Baggies head coach told BBC WM.
"We had a meeting yesterday. The deal is agreed with him but we have that situation with Everton.
"There is a little clause. I spoke to the board and we are doing everything we can.
"He would be a major boost for us and one that comes from within too. He already knows the place and most of the players.
"We have a lot of young players. At times they need the kind of support that he can bring."
Barry made 155 appearances and scored five goals for Everton across his four years with the club, following a move from Man City.
