With the official opening of the window upcoming on January 3rd, Royals manager Clarke highlighted his short period of working with the squad currently at his disposal as a factor in assessing where he can strengthen the team.
Speaking to the Official Club Website, the Scot also noted the restrictions of Financial Fair Play, casting doubt over the chances of signing the likes of ex-loanee Glenn Murray.
"January is a difficult month, and for me it's even harder because I've only had ten days to work with this group. Some of them will play on Saturday in the FA Cup which will help me in terms of knowing the squad.
"I'm pleased with what I've got, there's quality here and there's more to come from them. Obviously if there's more we can do to add to the squad, we'll try.
"But I'm not going to make promises about big business in January because it's not a good window."
"You have to understand the restrictions of Financial Fair Play, which the club have explained to me. It's a club that two years ago was in the Premier League, so you have to adapt from that period.
"There's not millions to spend because only the top clubs in the Premier League can do that now. You have to be prudent."
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